Revert "mm: vmalloc: support more granular vrealloc() sizing"

This reverts commit 2910019b which is
commit a0309faf upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I6e4ea0fd56032a331849525d3342d9679e3a384d
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>