st/nine: Fix CALLNZ implementation

st/nine: Fix CALLNZ implementation

Nothing seems to indicates the negation modifier would be stored in the
instruction flags instead of the source modifier. tx_src_param has
already handled it if it is in the source modifier.

In addition,
when the card supports native integers, the boolean
are stored in 32 bits int and are equal to
0 or 0xFFFFFFFF.

Given 0xFFFFFFFF is NaN if it was a float, better use
UIF than IF.

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Axel Davy <axel.davy@ens.fr>