mtd: do not duplicate length and offset checks in drivers

We already verify that offset and length are within the MTD device size
in the MTD API functions. Let's remove the duplicated checks in drivers.
This patch only affects the following API's:

'mtd_erase()'
'mtd_point()'
'mtd_unpoint()'
'mtd_get_unmapped_area()'
'mtd_read()'
'mtd_write()'
'mtd_panic_write()'
'mtd_lock()'
'mtd_unlock()'
'mtd_is_locked()'
'mtd_block_isbad()'
'mtd_block_markbad()'

This patch adds a bit of noise by removing too sparse empty lines, but this is
not too bad.

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

drivers/mtd/devices/mtd_dataflash.c

@@ -164,9 +164,6 @@ static int dataflash_erase(struct mtd_info *mtd, struct erase_info *instr)
 	      dev_name(&spi->dev), (long long)instr->addr,
 	      (long long)instr->len);
 
-	/* Sanity checks */
-	if (instr->addr + instr->len > mtd->size)
-		return -EINVAL;
 	div_u64_rem(instr->len, priv->page_size, &rem);
 	if (rem)
 		return -EINVAL;
@@ -257,8 +254,6 @@ static int dataflash_read(struct mtd_info *mtd, loff_t from, size_t len,
 	/* Sanity checks */
 	if (!len)
 		return 0;
-	if (from + len > mtd->size)
-		return -EINVAL;
 
 	/* Calculate flash page/byte address */
 	addr = (((unsigned)from / priv->page_size) << priv->page_offset)
@@ -333,8 +328,6 @@ static int dataflash_write(struct mtd_info *mtd, loff_t to, size_t len,
 	/* Sanity checks */
 	if (!len)
 		return 0;
-	if ((to + len) > mtd->size)
-		return -EINVAL;
 
 	spi_message_init(&msg);