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 <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/syscall.h

@@ -95,6 +95,6 @@ static inline int syscall_get_arch(void)
 	if (test_tsk_thread_flag(current, TIF_31BIT))
 		return AUDIT_ARCH_S390;
 #endif
-	return sizeof(long) == 8 ? AUDIT_ARCH_S390X : AUDIT_ARCH_S390;
+	return AUDIT_ARCH_S390X;
 }
 #endif	/* _ASM_SYSCALL_H */