alpha: Add syscall_get_return_value()

audit now requires syscall_get_return_value instead of regs_return_value
to retrieve syscall return code . Other architectures that support audit
have already define this function.
Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Matt Turner <mattst88@gmail.com>

arch/alpha/include/asm/syscall.h

@@ -9,4 +9,10 @@ static inline int syscall_get_arch(struct task_struct *task)
 	return AUDIT_ARCH_ALPHA;
 }
 
+static inline long syscall_get_return_value(struct task_struct *task,
+					    struct pt_regs *regs)
+{
+	return regs->r0;
+}
+
 #endif	/* _ASM_ALPHA_SYSCALL_H */