target-arm: convert NEON VZIP/VUZP/VTRN helper functions to pure TCG

target-arm: convert NEON VZIP/VUZP/VTRN helper functions to pure TCG

The neon_trn_u8, neon_trn_u16, neon_unzip_u8, neon_zip_u8 and neon_zip_u16
helpers used fixed registers to return values. This patch replaces that with
TCG code, so T0/T1 is no longer directly used by the helper functions.

Bugs in the gen_neon_unzip register load code were also fixed.

Signed-off-by: Filip Navara <filip.navara@gmail.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>