x86/pkeys/selftests: Save off 'prot' for allocations

x86/pkeys/selftests: Save off 'prot' for allocations

BugLink: http://bugs.launchpad.net/bugs/1794889
[ Upstream commit acb25d761d6f2f64e785ccefc71e54f244f1eda4 ]

This makes it possible to to tell what 'prot' a given allocation
is supposed to have.  That way, if we want to change just the
pkey, we know what 'prot' to pass to mprotect_pkey().

Also, keep a record of the most recent allocation so the tests
can easily find it.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellermen <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180509171354.AA23E228@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>