freedreno/ir3: handle input/output component

freedreno/ir3: handle input/output component

After the mesa/st nir linking support, we start to see inputs/outputs
like:

   decl_var shader_out INTERP_MODE_NONE float packed:uv (VARYING_SLOT_VAR9.x, 1, 0)
   decl_var shader_out INTERP_MODE_NONE float packed:uv@0 (VARYING_SLOT_VAR9.y, 1, 0)

(ie. were location_frac != .x)

Unfortunately I overlooked the addition of the component parameter to
load_input/store_output, so when we started encountering inputs/outputs
with component other than .x, we'd end up loading/storing the wrong
input/output.

Signed-off-by: Rob Clark <robdclark@gmail.com>