mm/vmalloc: fix a typo in comment

There is a typo in comment, fix it.
"exeeds" -> "exceeds"

Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200404060136.10838-1-hqjagain@gmail.com


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