Revert "selinux: Relocate selinux_enforcing to a separate 4k page"

This reverts commit c58c561f.

That out of tree patch causes the resulting kernel image to be too
large, causing ld.lld to error; since .bss is specified twice.

Fixes the observed error:
ld.lld: error: output file too large: 18446743524330100280 bytes

when using LLD without LTO enabled.

Bug: 151154720
Reported-by: Matthias Maennich <maennich@google.com>
Debugged-by: Fangrui Song <maskray@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Change-Id: Ib3a0a86d7d863e8e10d23359b19462d46f127dff