While debugging a gcc C testsuite failure on the aarch64 simulator, I
noticed that the support for FP stur instructions is broken.  They
accidentally have the two register operands swapped.  The problem can
be seen by comparing them with the equivalent FP str instructions.

I tested the fix by running the gcc C testsuite.  I get 3122
unexpected failures without the patch and 2856 unexpected failures
with the patch.

Jim