freedreno/ir3: Fix the type of half-float indirect uniform loads.

freedreno/ir3: Fix the type of half-float indirect uniform loads.

We would be making a MOV from a u32, when we should be loading from a
16-bit value.  This likely didn't bite us because we only do mediump in FS
and CS so far, and indirect uniforms are usually in a VS (and usually
highp).

Reviewed-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6179>