Add AArch32 to AArch64 register sychronization functions.
Replace manual register synchronization with new functions in
aarch64_cpu_do_interrupt() and HELPER(exception_return)().
Backports commit ce02049dbf1828b4bc77d921b108a9d84246e5aa from qemu
The helper functions for FRECPS and FRSQRTS have special case
handling that includes checks for zero inputs, so squash input
denormals if necessary before those checks. This fixes incorrect
output when the FPCR DZ bit is set to enable squashing of input
denormals.
Backports commit a8eb6e19991d1a7a6a7b04ac447548d30d75eb4a from qemu
