msm: mdss: update bist ctrl property as optional property

bist ctrl property is optional for DSI 1.4. Handle it
accordingly.

Change-Id: Ic0d0a0c25626e44ab3840bb2d9f34affbed01cea
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>

Documentation/devicetree/bindings/fb/mdss-dsi-ctrl.txt

@@ -22,8 +22,6 @@ Required properties:
 					regulator settings. It use 5 bytes for thulium pll.
 - qcom,platform-strength-ctrl:		An array of length 2 or 10 that specifies the PHY
 					strengthCtrl settings. It use 10 bytes for thulium pll.
-- qcom,platform-bist-ctrl:		An array of length 6 that specifies the PHY
-					BIST ctrl settings.
 - qcom,platform-lane-config:		An array of length 45 or 20 that specifies the PHY
 					lane configuration settings. It use 20 bytes for thulium pll.
 - qcom,dsi-pref-prim-pan:		phandle that specifies the primary panel to be used
@@ -34,6 +32,8 @@ Optional properties:
 
 - reg-names: 				A list of strings that map in order to the list of regs.
 					"dsi_phy_regulator" - MDSS DSI PHY REGULATOR region
+- qcom,platform-bist-ctrl:		An array of length 6 that specifies the PHY
+					BIST ctrl settings.
 - vcca-supply:				Phandle for vcca regulator device node.
 - qcom,ctrl-supply-entries:		A node that lists the elements of the supply used by the
 					DSI controller and PHY. There can be more than one instance

drivers/video/fbdev/msm/mdss_dsi.c

@@ -1842,15 +1842,12 @@ int dsi_panel_device_register(struct device_node *pan_node,
 
 	data = of_get_property(ctrl_pdev->dev.of_node,
 		"qcom,platform-bist-ctrl", &len);
-	if ((!data) || (len != 6)) {
+	if ((!data) || (len != 6))
 		pr_err("%s:%d, Unable to read Phy Bist Ctrl settings\n",
 			__func__, __LINE__);
-		return -EINVAL;
-	}
-
-	for (i = 0; i < len; i++) {
-		pinfo->mipi.dsi_phy_db.bistctrl[i] = data[i];
-	}
+	else
+		for (i = 0; i < len; i++)
+			pinfo->mipi.dsi_phy_db.bistctrl[i] = data[i];
 
 	data = of_get_property(ctrl_pdev->dev.of_node,
 		"qcom,platform-lane-config", &len);