target-arm: A64: Add 1-source 32-to-32 and 64-to-64 FP instructions

target-arm: A64: Add 1-source 32-to-32 and 64-to-64 FP instructions

This patch adds support for those instructions in the  "Floating-point
data-processing (1 source)" group which are simple 32-bit-to-32-bit
or 64-bit-to-64-bit operations (ie everything except FCVT between
single/double/half precision).

We put the new round-to-int helpers in helper.c because they will
also be used by the new ARMv8 A32/T32 rounding instructions.

Signed-off-by: Alexander Graf <agraf@suse.de>
[WN: Commit message tweak, merged single and double precision patches,
 updated to new infrastructure.]
Signed-off-by: Will Newton <will.newton@linaro.org>
[PMM: reworked decode, split FCVT out into their own patch]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>