selftests/mm: ensure pkey-*.h define inline functions only

selftests/mm: ensure pkey-*.h define inline functions only

Headers should not define non-inline functions, as this prevents them from
being included more than once in a given program.  pkey-helpers.h and the
arch-specific headers it includes currently define multiple such
non-inline functions.

In most cases those functions can simply be made inline - this patch does
just that.  read_ptr() is an exception as it must not be inlined.  Since
it is only called from protection_keys.c, we just move it there.

Link: https://lkml.kernel.org/r/20241209095019.1732120-9-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Keith Lucas <keith.lucas@oracle.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>