vkd3d-shader/d3d-asm: Print brackets around normalized io registers' first index.
SM6 bytecode has the particularity that IO register indexes have the following order: [i][p][e]. Where i is the array index, p is the control point index, and e is the element signature index.
But our d3d_asm_compile() function doesn't draw brackets around the first of these indexes, so for instance, array element 2 of input signature element 5 looks like: v2[5].
Which is prone to cause confusion since it looks like it is referring to signature element 2.
Same happens when there is a control point index.
So, to avoid potential confusion, let's just draw brackets around all indexes for normalized io registers.