lib/crc32: update the comments of crc32_{be,le}_generic()

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change-Id: Ia400c61bf7c9a49d3ea82fd1ce0ec35bfe4860c3