Make mips generated assembler more like the mips64 stuff.

I broke the mips build yesterday because it doesn't use
<private/bionic_asm.h> like the other architectures, including mips64.
I want to move mips closer to mips64 to try to avoid this kind of thing
in future.

Change-Id: Idb985587ff355b9e5e765c1f5671dc0144cd2488

libc/arch-mips/syscalls/__reboot.S

@@ -1,6 +1,8 @@
 /* Generated by gensyscalls.py. Do not edit. */
 
 #include <asm/unistd.h>
+#include <machine/asm.h>
+#include <machine/regdef.h>
     .text
     .globl __reboot
     .align 4
@@ -8,16 +10,16 @@
 
 __reboot:
     .set noreorder
-    .cpload $t9
-    li $v0, __NR_reboot
+    .cpload t9
+    li v0, __NR_reboot
     syscall
-    bnez $a3, 1f
-    move $a0, $v0
-    j $ra
+    bnez a3, 1f
+    move a0, v0
+    j ra
     nop
 1:
-    la $t9,__set_errno
-    j $t9
+    la t9,__set_errno
+    j t9
     nop
     .set reorder
     .end __reboot