intel/compiler: make sure swizzle is applied to if condition

This fixes a hang in the following piglit test when GCM moves a
UBO load outside of the loop.

tests/shaders/ssa/fs-if-def-else-break.shader_test

The end NIR ends up looking like this:

	vec2 32 ssa_3 = intrinsic load_ubo (ssa_2, ssa_0) (0, 1073741824, 0, 0, 8)
	vec1 32 ssa_4 = mov ssa_3.x
	vec1 32 ssa_5 = inot ssa_3.y
	/* succs: block_1 */
	loop {
           ...
           if ssa_5 { }
        }

Fixes: 1edf67fc3f ("intel/fs: Generate if instructions with inverted conditions")

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12064>

src/intel/compiler/brw_fs_nir.cpp

@@ -359,6 +359,7 @@ fs_visitor::nir_emit_if(nir_if *if_stmt)
    if (cond != NULL && cond->op == nir_op_inot) {
       invert = true;
       cond_reg = get_nir_src(cond->src[0].src);
+      cond_reg = offset(cond_reg, bld, cond->src[0].swizzle[0]);
    } else {
       invert = false;
       cond_reg = get_nir_src(if_stmt->condition);