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