i965/vec4: dump subnr for FIXED_GRF

This came in handy when debugging the payload setup for Tess Eval,
since it prints correct subnr for attributes that can be loaded
in the second half of a register.

Reviewed-by: Matt Turner <mattst88@gmail.com>
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index 6bc6f48..9f6d9a8 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -1562,7 +1562,7 @@
          fprintf(file, "vgrf%d", inst->src[i].nr);
          break;
       case FIXED_GRF:
-         fprintf(file, "g%d", inst->src[i].nr);
+         fprintf(file, "g%d.%d", inst->src[i].nr, inst->src[i].subnr);
          break;
       case ATTR:
          fprintf(file, "attr%d", inst->src[i].nr);