[MIPS] Rename MIPS sys_pipe syscall entry point to something MIPS-specific.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/syscall.c

@@ -40,7 +40,14 @@
 #include <asm/sysmips.h>
 #include <asm/uaccess.h>
 
-asmlinkage int sys_pipe(nabi_no_regargs volatile struct pt_regs regs)
+/*
+ * For historic reasons the pipe(2) syscall on MIPS has an unusual calling
+ * convention.  It returns results in registers $v0 / $v1 which means there
+ * is no need for it to do verify the validity of a userspace pointer
+ * argument.  Historically that used to be expensive in Linux.  These days
+ * the performance advantage is negligible.
+ */
+asmlinkage int sysm_pipe(nabi_no_regargs volatile struct pt_regs regs)
 {
 	int fd[2];
 	int error, res;