mtd: remove extra retlen assignment

MTD functions always assign the 'retlen' argument to 0 at the very
beginning - the callers do not have to do this.

I used the following semantic patch to find these places:

@@
identifier retlen;
expression a, b, c, d, e;
constant C;
type T;
@@
(
- retlen = C;
|
T
-retlen = C
+ retlen
;
)

... when != retlen
    when exists

(
mtd_read(a, b, c, &retlen, d)
|
mtd_write(a, b, c, &retlen, d)
|
mtd_panic_write(a, b, c, &retlen, d)
|
mtd_point(a, b, c, &retlen, d, e)
|
mtd_read_fact_prot_reg(a, b, c, &retlen, d)
|
mtd_write_user_prot_reg(a, b, c, &retlen, d)
|
mtd_read_user_prot_reg(a, b, c, &retlen, d)
|
mtd_writev(a, b, c, d, &retlen)
)

I ran it twice, because there were cases of double zero assigments
in mtd tests. Then I went through the patch to verify that spatch
did not find any false positives.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/tests/mtd_subpagetest.c

@@ -115,7 +115,7 @@ static int erase_whole_device(void)
 
 static int write_eraseblock(int ebnum)
 {
-	size_t written = 0;
+	size_t written;
 	int err = 0;
 	loff_t addr = ebnum * mtd->erasesize;
 
@@ -150,7 +150,7 @@ static int write_eraseblock(int ebnum)
 
 static int write_eraseblock2(int ebnum)
 {
-	size_t written = 0;
+	size_t written;
 	int err = 0, k;
 	loff_t addr = ebnum * mtd->erasesize;
 
@@ -189,13 +189,12 @@ static void print_subpage(unsigned char *p)
 
 static int verify_eraseblock(int ebnum)
 {
-	size_t read = 0;
+	size_t read;
 	int err = 0;
 	loff_t addr = ebnum * mtd->erasesize;
 
 	set_random_data(writebuf, subpgsize);
 	clear_data(readbuf, subpgsize);
-	read = 0;
 	err = mtd_read(mtd, addr, subpgsize, &read, readbuf);
 	if (unlikely(err || read != subpgsize)) {
 		if (mtd_is_bitflip(err) && read == subpgsize) {
@@ -223,7 +222,6 @@ static int verify_eraseblock(int ebnum)
 
 	set_random_data(writebuf, subpgsize);
 	clear_data(readbuf, subpgsize);
-	read = 0;
 	err = mtd_read(mtd, addr, subpgsize, &read, readbuf);
 	if (unlikely(err || read != subpgsize)) {
 		if (mtd_is_bitflip(err) && read == subpgsize) {
@@ -252,7 +250,7 @@ static int verify_eraseblock(int ebnum)
 
 static int verify_eraseblock2(int ebnum)
 {
-	size_t read = 0;
+	size_t read;
 	int err = 0, k;
 	loff_t addr = ebnum * mtd->erasesize;
 
@@ -261,7 +259,6 @@ static int verify_eraseblock2(int ebnum)
 			break;
 		set_random_data(writebuf, subpgsize * k);
 		clear_data(readbuf, subpgsize * k);
-		read = 0;
 		err = mtd_read(mtd, addr, subpgsize * k, &read, readbuf);
 		if (unlikely(err || read != subpgsize * k)) {
 			if (mtd_is_bitflip(err) && read == subpgsize * k) {
@@ -288,14 +285,13 @@ static int verify_eraseblock2(int ebnum)
 static int verify_eraseblock_ff(int ebnum)
 {
 	uint32_t j;
-	size_t read = 0;
+	size_t read;
 	int err = 0;
 	loff_t addr = ebnum * mtd->erasesize;
 
 	memset(writebuf, 0xff, subpgsize);
 	for (j = 0; j < mtd->erasesize / subpgsize; ++j) {
 		clear_data(readbuf, subpgsize);
-		read = 0;
 		err = mtd_read(mtd, addr, subpgsize, &read, readbuf);
 		if (unlikely(err || read != subpgsize)) {
 			if (mtd_is_bitflip(err) && read == subpgsize) {