drm/radeon/kms: respect single crtc cards, only create one crtc. (v2)

Also add single crtc for RN50 chips.

changes in v2:
fix vblank init to respect single crtc flag
fix r100 mode bandwidth to respect single crtc flag

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_fb.c b/drivers/gpu/drm/radeon/radeon_fb.c
index 1ba704e..325e40b 100644
--- a/drivers/gpu/drm/radeon/radeon_fb.c
+++ b/drivers/gpu/drm/radeon/radeon_fb.c
@@ -146,6 +146,7 @@
 	unsigned long tmp;
 	bool fb_tiled = false; /* useful for testing */
 	u32 tiling_flags = 0;
+	int crtc_count;
 
 	mode_cmd.width = surface_width;
 	mode_cmd.height = surface_height;
@@ -217,7 +218,11 @@
 	rfbdev = info->par;
 	rfbdev->helper.funcs = &radeon_fb_helper_funcs;
 	rfbdev->helper.dev = dev;
-	ret = drm_fb_helper_init_crtc_count(&rfbdev->helper, 2,
+	if (rdev->flags & RADEON_SINGLE_CRTC)
+		crtc_count = 1;
+	else
+		crtc_count = 2;
+	ret = drm_fb_helper_init_crtc_count(&rfbdev->helper, crtc_count,
 					    RADEONFB_CONN_LIMIT);
 	if (ret)
 		goto out_unref;