tree-wide: convert open calls to remove spaces to skip_spaces() lib function

Makes use of skip_spaces() defined in lib/string.c for removing leading
spaces from strings all over the tree.

It decreases lib.a code size by 47 bytes and reuses the function tree-wide:
   text    data     bss     dec     hex filename
  64688     584     592   65864   10148 (TOTALS-BEFORE)
  64641     584     592   65817   10119 (TOTALS-AFTER)

Also, while at it, if we see (*str && isspace(*str)), we can be sure to
remove the first condition (*str) as the second one (isspace(*str)) also
evaluates to 0 whenever *str == 0, making it redundant. In other words,
"a char equals zero is never a space".

Julia Lawall tried the semantic patch (http://coccinelle.lip6.fr) below,
and found occurrences of this pattern on 3 more files:
    drivers/leds/led-class.c
    drivers/leds/ledtrig-timer.c
    drivers/video/output.c

@@
expression str;
@@

( // ignore skip_spaces cases
while (*str &&  isspace(*str)) { \(str++;\|++str;\) }
|
- *str &&
isspace(*str)
)

Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Cc: Julia Lawall <julia@diku.dk>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Neil Brown <neilb@suse.de>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: David Howells <dhowells@redhat.com>
Cc: <linux-ext4@vger.kernel.org>
Cc: Samuel Ortiz <samuel@sortiz.org>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/kernel/cpu/mtrr/if.c

@@ -4,6 +4,7 @@
 #include <linux/proc_fs.h>
 #include <linux/module.h>
 #include <linux/ctype.h>
+#include <linux/string.h>
 #include <linux/init.h>
 
 #define LINE_SIZE 80
@@ -133,8 +134,7 @@ mtrr_write(struct file *file, const char __user *buf, size_t len, loff_t * ppos)
 		return -EINVAL;
 
 	base = simple_strtoull(line + 5, &ptr, 0);
-	while (isspace(*ptr))
-		ptr++;
+	ptr = skip_spaces(ptr);
 
 	if (strncmp(ptr, "size=", 5))
 		return -EINVAL;
@@ -142,14 +142,11 @@ mtrr_write(struct file *file, const char __user *buf, size_t len, loff_t * ppos)
 	size = simple_strtoull(ptr + 5, &ptr, 0);
 	if ((base & 0xfff) || (size & 0xfff))
 		return -EINVAL;
-	while (isspace(*ptr))
-		ptr++;
+	ptr = skip_spaces(ptr);
 
 	if (strncmp(ptr, "type=", 5))
 		return -EINVAL;
-	ptr += 5;
-	while (isspace(*ptr))
-		ptr++;
+	ptr = skip_spaces(ptr + 5);
 
 	for (i = 0; i < MTRR_NUM_TYPES; ++i) {
 		if (strcmp(ptr, mtrr_strings[i]))