register_state_check.h: add compiler barrier
around ASM_REGISTER_STATE_CHECK() this helps keep the call ordering
consistent avoiding some code reordering which may affect the registers
being checked
fixes issue with armv7 and multiple versions of gcc:
[ RUN ] C/AddNoiseTest.CheckNoiseAdded/0
test/register_state_check.h:116: Failure
Expected equality of these values:
pre_store_[i]
Which is: 0
post_store[i]
Which is:
4618441417868443648
Bug: webm:1760
Change-Id: Ib8bcefd2c4d263f9fc4d4b4d4ffb853fe89d1152
Fixed: webm:1760