Add vmov between integers and floats in ARM assembler.

Adds vmovrs that implements moving from an integer (GP) register and a
float (S) register to the integrated ARM assembler.

The test also shows that moving from a float (S) register to an
integer (GP) register also works.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4334
R=eholk@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/1647683002 .