[MIPS] Fix mips32r1 build

Fix regression from 6701fbe5f0d799c5245b0cdf3a69ecdcbfd9fb08 .
The rdhwr instruction is unsupported by mips32r1 cpus, but is
supported via kernel emulation on those cpus.

Change-Id: Ieb3343fff0f0da54003044f451c90e1c761208eb
diff --git a/opengl/libs/GLES_CM/gl.cpp b/opengl/libs/GLES_CM/gl.cpp
index 0b30956..b1b31f8 100644
--- a/opengl/libs/GLES_CM/gl.cpp
+++ b/opengl/libs/GLES_CM/gl.cpp
@@ -219,6 +219,7 @@
         asm volatile(                                            \
             ".set  push\n\t"                                     \
             ".set  noreorder\n\t"                                \
+            ".set  mips32r2\n\t"                                 \
             "rdhwr %[tls], $29\n\t"                              \
             "lw    %[t0], %[OPENGL_API](%[tls])\n\t"             \
             "beqz  %[t0], 1f\n\t"                                \