target/arm: Convert VFP round insns to decodetree

target/arm: Convert VFP round insns to decodetree

Convert the VFP round-to-integer instructions VRINTR, VRINTZ and
VRINTX to decodetree.

These instructions were only introduced as part of the "VFP misc"
additions in v8A, so we check this. The old decoder's implementation
was incorrectly providing them even for v7A CPUs.

Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>