i965/nir: fix check to resolve booleans to work with sized nir_alu_type

i965/nir: fix check to resolve booleans to work with sized nir_alu_type

As nir_alu_type has now embedded the data size, the check for the
instruction's output type (to see if a boolean resolve is required)
should ignore the data size part.

Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>