radeon drivers: handle PIPE_CAP_MAX_VIEWPORTS

src/gallium/drivers/r300/r300_screen.c

@@ -192,6 +192,9 @@ static int r300_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
             return 4;
 	case PIPE_CAP_ENDIANNESS:
             return PIPE_ENDIAN_LITTLE;
+
+        case PIPE_CAP_MAX_VIEWPORTS:
+            return 1;
     }
     return 0;
 }

src/gallium/drivers/r600/r600_pipe.c

@@ -651,6 +651,9 @@ static int r600_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
 		/* XXX some r6xx are buggy and can only do 4 */
 		return 8;
 
+	case PIPE_CAP_MAX_VIEWPORTS:
+		return 1;
+
 	/* Timer queries, present when the clock frequency is non zero. */
 	case PIPE_CAP_QUERY_TIME_ELAPSED:
 		return rscreen->b.info.r600_clock_crystal_freq != 0;

src/gallium/drivers/radeonsi/radeonsi_pipe.c

@@ -438,6 +438,9 @@ static int r600_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
 		/* FIXME some r6xx are buggy and can only do 4 */
 		return 8;
 
+	case PIPE_CAP_MAX_VIEWPORTS:
+		return 1;
+
 	/* Timer queries, present when the clock frequency is non zero. */
 	case PIPE_CAP_QUERY_TIMESTAMP:
 	case PIPE_CAP_QUERY_TIME_ELAPSED: