Revert "selftests: mm: fix map_hugetlb failure on 64K page size systems"

This reverts commit 0d29b474 which is
commit 91b80cc5 upstream.

map_hugetlb.c:18:10: fatal error: vm_util.h: No such file or directory
   18 | #include "vm_util.h"
      |          ^~~~~~~~~~~
compilation terminated.

vm_util.h is not present in 5.15.y, as commit:642bc52a

 ("selftests:
vm: bring common functions to a new file") is not present in stable
kernels <=6.1.y

Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>