[MIPS] Fix a problem with the FPU double alignment workaround.

This patch fixes the following cts failure:
tests.api.java.lang.reflect.MethodTest#test_invokeLjava_lang_Object$Ljava_lang_Object

Change-Id: If29c138418a3df6e195947c8e3d80f2cfd6aa9db
Signed-off-by: Douglas Leung <douglas@mips.com>