selftests/vm/pkeys: override access right definitions on powerpc

Some platforms hardcode the x86 values for PKEY_DISABLE_ACCESS
and PKEY_DISABLE_WRITE such as those in:
 /usr/include/bits/mman-shared.h.

This overrides the definitions with correct values for powerpc.

[sandipan@linux.ibm.com: fix powerpc access right definitions]
  Link: http://lkml.kernel.org/r/1ba86fd8a94f38131cfe2d9f277001dd1ad1d34e.1588959697.git.sandipan@linux.ibm.comSigned-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: "Desnes A. Nunes do Rosario" <desnesn@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Suchanek <msuchanek@suse.de>
Cc: Shuah Khan <shuah@kernel.org>
Link: http://lkml.kernel.org/r/f6eb38cb3a1e12eb2cdc9da6300bc5a5dfba0db9.1585646528.git.sandipan@linux.ibm.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/selftests/vm/pkey-powerpc.h

@@ -16,13 +16,11 @@
 #define fpregs			fp_regs
 #define si_pkey_offset		0x20
 
-#ifndef PKEY_DISABLE_ACCESS
-# define PKEY_DISABLE_ACCESS	0x3  /* disable read and write */
-#endif
+#undef PKEY_DISABLE_ACCESS
+#define PKEY_DISABLE_ACCESS	0x3  /* disable read and write */
 
-#ifndef PKEY_DISABLE_WRITE
-# define PKEY_DISABLE_WRITE	0x2
-#endif
+#undef PKEY_DISABLE_WRITE
+#define PKEY_DISABLE_WRITE	0x2
 
 #define NR_PKEYS		32
 #define NR_RESERVED_PKEYS_4K	27 /* pkey-0, pkey-1, exec-only-pkey