target-arm: Don't permit ARMv8-only Neon insns on ARMv7

target-arm: Don't permit ARMv8-only Neon insns on ARMv7

The Neon instructions VCVTA, VCVTM, VCVTN, VCVTP, VRINTA, VRINTM,
VRINTN, VRINTP, VRINTX, and VRINTZ were only introduced with ARMv8,
so they need a guard to make them UNDEF if the CPU only supports ARMv7.
(We got this right for all the other new-in-v8 insns, but forgot
it for these Neon 2-reg-misc ops.)

Reported-by: Christophe Lyon <[email protected]>
Tested-by: Christophe Lyon <[email protected]>
Signed-off-by: Peter Maydell <[email protected]>
Message-id: 1465492511[email protected]