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

This reverts commit a584c773 which is
commit 91b80cc5 upstream.

This fixes the following build error:

map_hugetlb.c: In function 'main':
map_hugetlb.c:79:25: warning: implicit declaration of function 'default_huge_page_size' [-Wimplicit-function-declaration]
79 |         hugepage_size = default_huge_page_size();

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>