target/arm: Use pointers in neon zip/uzp helpers

target/arm: Use pointers in neon zip/uzp helpers

Rather than passing regnos to the helpers, pass pointers to the
vector registers directly.  This eliminates the need to pass in
the environment pointer and reduces the number of places that
directly access env->vfp.regs[].

Reviewed-by: Peter Maydell <[email protected]>
Signed-off-by: Richard Henderson <[email protected]>
Reviewed-by: Alex Bennée <[email protected]>
Message-id: 20180119045438[email protected]
Signed-off-by: Peter Maydell <[email protected]>