ir3: Consider dst type in ubo_vec4 to ldc lowering

ir3: Consider dst type in ubo_vec4 to ldc lowering

The dst type could be either 16b or 32b.

Fixes validation failure in dEQP-VK.subgroups.* tests which deal with
16b types.

 validation fail: (type_size(instr->cat6.type) <= 16) == !!((instr->dsts[0])->flags & IR3_REG_HALF)
   -> for instruction: MESA: info: 0023:0000:000:        ldc.offset0.base0 hssa_23 (wrmask=0x3), ssa_1, ssa_22

Signed-off-by: Danylo Piliaiev <dpiliaiev@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21316>