nir/builder: Add a nir_ieq_imm helper

This shows up surprisingly often.

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6332>

src/compiler/glsl/glsl_to_nir.cpp

@@ -2302,7 +2302,7 @@ nir_visitor::visit(ir_expression *ir)
       result = nir_channel(&b, srcs[0], 0);
       for (unsigned i = 1; i < ir->operands[0]->type->vector_elements; i++) {
          nir_ssa_def *swizzled = nir_channel(&b, srcs[0], i);
-         result = nir_bcsel(&b, nir_ieq(&b, srcs[1], nir_imm_int(&b, i)),
+         result = nir_bcsel(&b, nir_ieq_imm(&b, srcs[1], i),
                             swizzled, result);
       }
       break;