powerpc: add pkey syscall numbers from linux v4.16

add pkey_mprotect, pkey_alloc, pkey_free syscall numbers,
new in linux commits 3350eb2ea127978319ced883523d828046af4045
and 9499ec1b5e82321829e1c1510bcc37edc20b6f38

arch/powerpc/bits/syscall.h.in

@@ -368,4 +368,7 @@
 #define __NR_pwritev2              381
 #define __NR_kexec_file_load       382
 #define __NR_statx                 383
+#define __NR_pkey_alloc            384
+#define __NR_pkey_free             385
+#define __NR_pkey_mprotect         386
 

arch/powerpc64/bits/syscall.h.in

@@ -359,4 +359,7 @@
 #define __NR_pwritev2               381
 #define __NR_kexec_file_load        382
 #define __NR_statx                  383
+#define __NR_pkey_alloc             384
+#define __NR_pkey_free              385
+#define __NR_pkey_mprotect          386