mm/vmalloc.c: fix the comment of find_vm_area

Fix the comment of find_vm_area() and get_vm_area()

Signed-off-by: Hui Su <sh_def@163.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/20200927153034.GA199877@rlk


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>