drm/omap: fix omap_framebuffer_unpin() error handling

omap_framebuffer_unpin() check the return value of omap_gem_put_paddr()
and return immediately if omap_gem_put_paddr() fails.

This patch removes the check for the return value, and also removes the
return value of omap_framebuffer_unpin(), because:

 * Nothing checks the return value of omap_framebuffer_unpin(), and even
   something did check it, there's nothing the caller can do to handle
   the error.

 * If a omap_gem_put_paddr() fails, the framebuffer's other planes will
   be left unreleased. So it's better to call omap_gem_put_paddr() for
   all the planes, even if one would fail.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
diff --git a/drivers/gpu/drm/omapdrm/omap_drv.h b/drivers/gpu/drm/omapdrm/omap_drv.h
index ae2df41..2ef89c0 100644
--- a/drivers/gpu/drm/omapdrm/omap_drv.h
+++ b/drivers/gpu/drm/omapdrm/omap_drv.h
@@ -177,7 +177,7 @@
 		struct drm_mode_fb_cmd2 *mode_cmd, struct drm_gem_object **bos);
 struct drm_gem_object *omap_framebuffer_bo(struct drm_framebuffer *fb, int p);
 int omap_framebuffer_pin(struct drm_framebuffer *fb);
-int omap_framebuffer_unpin(struct drm_framebuffer *fb);
+void omap_framebuffer_unpin(struct drm_framebuffer *fb);
 void omap_framebuffer_update_scanout(struct drm_framebuffer *fb,
 		struct omap_drm_window *win, struct omap_overlay_info *info);
 struct drm_connector *omap_framebuffer_get_next_connector(