x86/syscalls: Remove -Wno-override-init for syscall tables

Commit 44fe4895

 ("Stop filling syscall arrays with *_sys_ni_syscall")
removes the need for -Wno-override-init, since the table is now filled
sequentially instead of overriding a default value.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20210524181707.132844-3-brgerst@gmail.com