s390/syscalls: simplify syscall_get_arch()
s390/syscalls: simplify syscall_get_arch()

Given that sizeof(long) is now always 8, we can simplify syscall_get_arch()
a bit.
Just another piece I didn't find when removing 31 bit support.

Signed-off-by: Heiko Carstens <8dcf0f69152f32f23184f83357a3731522e56b9c@de.ibm.com>
Signed-off-by: Martin Schwidefsky <52616596d8f5df0d597e85ab515377f92f939c68@de.ibm.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs