selinux: don't use make's grouped targets feature yet

The Linux Kernel currently only requires make v3.82 while the grouped
target functionality requires make v4.3.  Removed the grouped target
introduced in 4ce1f694 ("selinux: ensure av_permissions.h is
built when needed") as well as the multiple header file targets in
the make rule.  This effectively reverts the problem commit.

We will revisit this change when make >= 4.3 is required by the rest
of the kernel.

Cc: stable@vger.kernel.org
Fixes: 4ce1f694 ("selinux: ensure av_permissions.h is built when needed")
Reported-by: Erwan Velu <e.velu@criteo.com>
Reported-by: Luiz Capitulino <luizcap@amazon.com>
Tested-by: Luiz Capitulino <luizcap@amazon.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>