s390/entry: align system call table on 8 bytes

commit 378ca2d2ad410a1cd5690d06b46c5e2297f4c8c0 upstream.

Align system call table on 8 bytes. With sys_call_table entry size
of 8 bytes that eliminates the possibility of a system call pointer
crossing cache line boundary.

Cc: stable@kernel.org
Suggested-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>