arch: add pkey and rseq syscall numbers everywhere

Most architectures define system call numbers for the rseq and pkey system
calls, even when they don't support the features, and perhaps never will.

Only a few architectures are missing these, so just define them anyway
for consistency. If we decide to add them later to one of these, the
system call numbers won't get out of sync then.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/alpha/kernel/syscalls/syscall.tbl

@@ -452,3 +452,7 @@
 521	common	pwritev2			sys_pwritev2
 522	common	statx				sys_statx
 523	common	io_pgetevents			sys_io_pgetevents
+524	common	pkey_mprotect			sys_pkey_mprotect
+525	common	pkey_alloc			sys_pkey_alloc
+526	common	pkey_free			sys_pkey_free
+527	common	rseq				sys_rseq