disp: msm: restrict AVR_STEP based on panel requirement

Some panels require a fixed step rate for a particular mode.
This change allows DSI panels to specify a single supported
step rate for each nominal fps rate which SDE will enforce
during atomic check of AVR parameters.

Change-Id: I049415449bc88ccd396fced16d4534251eac3a06
Signed-off-by: Steve Cohen <cohens@codeaurora.org>

msm/dsi/dsi_display.h

@@ -419,10 +419,18 @@ int dsi_display_get_default_lms(void *dsi_display, u32 *num_lm);
  * @display:            Handle to display.
  * @mode_fps:           Fps value of current mode
  *
- * Return: error code.
+ * Return: Qsync min fps rate or -ve error code.
  */
 int dsi_display_get_qsync_min_fps(void *dsi_display, u32 mode_fps);
 
+/**
+ * dsi_display_get_avr_step_req_fps() - get avr step rate for given fps
+ * @display:            Handle to display.
+ * @mode_fps:           Fps value of current mode
+ *
+ * Return: AVR step rate or -ve error code.
+ */
+int dsi_display_get_avr_step_req_fps(void *dsi_display, u32 mode_fps);
 
 /**
  * dsi_display_find_mode() - retrieve cached DSI mode given relevant params