Fix MI_INIT_MODE_REG bug.
Fix MI_INIT_MODE_REG bug.

MI_INIT_MODE, MI_EBUS_TEST_MODE and MI_RDRAM_REG_MODE bits
were begin unconditionally masked out, even when not explicitly
asked.

Thanks to bsmiles32 for pointing out this bug.

tj90241/cen64,tj90241/cen64,LuigiBlood/cen64,LuigiBlood/cen64