freedreno/ir3: handle scalarized varying inputs

freedreno/ir3: handle scalarized varying inputs

If the load_interpolated_input is scalarized, we would be too
conservative about deciding the tex instruction wasn't a candidate to
pre-fetch:

	vec1 32 ssa_0 = load_const (0x00000000 /* 0.000000 */)
	vec2 32 ssa_1 = intrinsic load_barycentric_pixel () (0) /* interp_mode=0 */
	vec1 32 ssa_2 = intrinsic load_interpolated_input (ssa_1, ssa_0) (0, 0) /* base=0 */ /* component=0 */	/* packed:v_uv,v_uv1 */
	vec1 32 ssa_3 = intrinsic load_interpolated_input (ssa_1, ssa_0) (0, 1) /* base=0 */ /* component=1 */	/* packed:v_uv,v_uv1 */
	vec2 32 ssa_8 = vec2 ssa_2, ssa_3
	vec4 32 ssa_9 = tex ssa_8 (coord), 0 (texture), 0 (sampler)

Really we don't care that the texcoord components come from different
load_interpolated_input instructions, just that they have consecutive
varying offsets.

Reported-by: Eduardo Lima Mitev <elima@igalia.com>
Reviewed-by: Eduardo Lima Mitev <elima@igalia.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>