MIPS64: Properly preserve $gp in art_quick_test_suspend

$gp register was restored in RESTORE_SAVE_EVERYTHING_CALLEE_SAVE_FRAME
with value from $t8, but $t8 has been clobbered in the meantime.

Calculation of $gp is done as a part of the macro
SETUP_SAVE_EVERYTHING_CALLEE_SAVE_FRAME. This allows us to use version
of .cpsetup where $gp is preserved on the stack, instead in another
register.

This fixes over 60 ART tests.

Additionally this suppresses assembler warnings for MIPS32 and MIPS64:
    Warning: used $at without ".set noat"

Test: mma test-art-target-run-test on QEMU

Change-Id: Ic92680c3cb2a4405353b3640c836e92c0231bd15
diff --git a/runtime/arch/mips/quick_entrypoints_mips.S b/runtime/arch/mips/quick_entrypoints_mips.S
index b926bdf..9b24128 100644
--- a/runtime/arch/mips/quick_entrypoints_mips.S
+++ b/runtime/arch/mips/quick_entrypoints_mips.S
@@ -352,8 +352,11 @@
 
     // Set up $gp, clobbering $ra and using the branch delay slot for a useful instruction.
     bal 1f
+    .set push
+    .set noat
     sw     $at, 144($sp)
     .cfi_rel_offset 1, 144
+    .set pop
 1:
     .cpload $ra
 
@@ -460,8 +463,11 @@
     .cfi_restore 3
     lw     $v0, 148($sp)
     .cfi_restore 2
+    .set push
+    .set noat
     lw     $at, 144($sp)
     .cfi_restore 1
+    .set pop
 
     addiu  $sp, $sp, 256            # pop frame
     .cfi_adjust_cfa_offset -256