radv: fix invalid element type when filling vertex input default values

The elements added into a vector should have the same type as the
first one, otherwise this hits an assertion in LLVM.

Fixes: 4b3549c084 ("radv: reduce the number of loaded channels for vertex input fetches")
reported-by: Philip Rebohle <philip.rebohle@tu-dortmund.de>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

src/amd/vulkan/radv_nir_to_llvm.c

@@ -2089,8 +2089,10 @@ radv_fixup_vertex_input_fetches(struct radv_shader_context *ctx,
 		elemtype = LLVMTypeOf(value);
 	}
 
-	for (unsigned i = num_channels; i < 4; i++)
+	for (unsigned i = num_channels; i < 4; i++) {
 		chan[i] = i == 3 ? one : zero;
+		chan[i] = ac_to_float(&ctx->ac, chan[i]);
+	}
 
 	return ac_build_gather_values(&ctx->ac, chan, 4);
 }