Unify our assembler macros.

Our <machine/asm.h> files were modified from upstream, to the extent
that no architecture was actually using the upstream ENTRY or END macros,
assuming that architecture even had such a macro upstream. This patch moves
everyone to the same macros, with just a few tweaks remaining in the
<machine/asm.h> files, which no one should now use directly.

I've removed most of the unused cruft from the <machine/asm.h> files, though
there's still rather a lot in the mips/mips64 ones.

Bug: 12229603
Change-Id: I2fff287dc571ac1087abe9070362fb9420d85d6d
diff --git a/libc/arch-mips/bionic/syscall.S b/libc/arch-mips/bionic/syscall.S
index af5bcc9..db477a5 100644
--- a/libc/arch-mips/bionic/syscall.S
+++ b/libc/arch-mips/bionic/syscall.S
@@ -26,11 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#include <asm/unistd.h>
-    .text
-    .globl syscall
-    .align 4
-    .ent syscall
+#include <private/bionic_asm.h>
 
 /*
  * The caller is only required to allocate 16 bytes of stack for a0-a3.
@@ -38,28 +34,28 @@
  */
 #define STACKSIZE 2*4
 
-syscall:
+ENTRY(syscall)
     .set noreorder
-    .cpload $t9
-    move    $v0, $a0
-    move    $a0, $a1
-    move    $a1, $a2
-    move    $a2, $a3
-    lw      $a3, 16($sp)
-    lw      $t0, 20($sp)
-    lw      $t1, 24($sp)
-    subu    $sp, STACKSIZE
-    sw      $t0, 16($sp)
-    sw      $t1, 20($sp)
+    .cpload t9
+    move    v0, a0
+    move    a0, a1
+    move    a1, a2
+    move    a2, a3
+    lw      a3, 16(sp)
+    lw      t0, 20(sp)
+    lw      t1, 24(sp)
+    subu    sp, STACKSIZE
+    sw      t0, 16(sp)
+    sw      t1, 20(sp)
     syscall
-    addu    $sp, STACKSIZE
-    bnez    $a3, 1f
-    move    $a0, $v0
-    j       $ra
+    addu    sp, STACKSIZE
+    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 syscall
+END(syscall)