r300: add PIPE_SHADER_CAP_MAX_HW_ATOMIC_COUNTER* switch cases

To silence compiler warnings.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
diff --git a/src/gallium/drivers/r300/r300_screen.c b/src/gallium/drivers/r300/r300_screen.c
index ac5208a..99d6302 100644
--- a/src/gallium/drivers/r300/r300_screen.c
+++ b/src/gallium/drivers/r300/r300_screen.c
@@ -434,6 +434,8 @@
         case PIPE_SHADER_CAP_MAX_SHADER_IMAGES:
         case PIPE_SHADER_CAP_LOWER_IF_THRESHOLD:
         case PIPE_SHADER_CAP_TGSI_SKIP_MERGE_REGISTERS:
+        case PIPE_SHADER_CAP_MAX_HW_ATOMIC_COUNTERS:
+        case PIPE_SHADER_CAP_MAX_HW_ATOMIC_COUNTER_BUFFERS:
             return 0;
         case PIPE_SHADER_CAP_MAX_UNROLL_ITERATIONS_HINT:
             return 32;