target/arm: Convert Neon 3-reg-same VADD/VSUB to decodetree

target/arm: Convert Neon 3-reg-same VADD/VSUB to decodetree

Convert the Neon 3-reg-same VADD and VSUB insns to decodetree.

Note that we don't need the neon_3r_sizes[op] check here because all
size values are OK for VADD and VSUB; we'll add this when we convert
the first insn that has size restrictions.

For this we need one of the GVecGen*Fn typedefs currently in
translate-a64.h; move them all to translate.h as a block so they
are visible to the 32-bit decoder.

Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Message-id: 20200430181003[email protected]