alpha: Fix up new futex syscall numbers

As per Arnd, Alpha syscalls since time64 are offset by 120, retain
this offset.

Fixes: 9f6c532 ("futex: Add sys_futex_wake()")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/cb4bb8e2-7dfe-4ca4-aa70-060f7b2f8f95@app.fastmail.com

arch/alpha/kernel/syscalls/syscall.tbl

@@ -492,6 +492,7 @@
 560	common	set_mempolicy_home_node		sys_ni_syscall
 561	common	cachestat			sys_cachestat
 562	common	fchmodat2			sys_fchmodat2
-563	common	futex_wake			sys_futex_wake
-564	common	futex_wait			sys_futex_wait
-565	common	futex_requeue			sys_futex_requeue
+# 563 reserved for map_shadow_stack
+564	common	futex_wake			sys_futex_wake
+565	common	futex_wait			sys_futex_wait
+566	common	futex_requeue			sys_futex_requeue