target/arm: Clear unused predicate bits for LD1RQ

target/arm: Clear unused predicate bits for LD1RQ

The 16-byte load only uses 16 predicate bits.  But while
reusing the other load infrastructure, we find other bits
that are set and trigger an assert.  To avoid this and
retain the assert, zero-extend the predicate that we pass
to the LD1 helper.

Tested-by: Laurent Desnogues <[email protected]>
Reported-by: Laurent Desnogues <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Signed-off-by: Richard Henderson <[email protected]>
Message-id: 20181005175350[email protected]
Signed-off-by: Peter Maydell <[email protected]>