drm/omap: Remove regulator API abuse

regulator_can_change_voltage() is deprecated and it's use is not necessary
as commit:
6a0028b3dd regulator: Deprecate regulator_can_change_voltage()
describers it clearly.

Also, regulator_set_voltage() is misused in the driver, as it is
supposed to be used only in cases where the regulator voltage needs to
be changed dynamically at runtime. In DSS's case, we always want a fixed
voltage, set in the .dts files.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/omapdrm/dss/dsi.c

@@ -1180,15 +1180,6 @@ static int dsi_regulator_init(struct platform_device *dsidev)
 		return PTR_ERR(vdds_dsi);
 	}
 
-	if (regulator_can_change_voltage(vdds_dsi)) {
-		r = regulator_set_voltage(vdds_dsi, 1800000, 1800000);
-		if (r) {
-			devm_regulator_put(vdds_dsi);
-			DSSERR("can't set the DSI regulator voltage\n");
-			return r;
-		}
-	}
-
 	dsi->vdds_dsi_reg = vdds_dsi;
 
 	return 0;

drivers/gpu/drm/omapdrm/dss/hdmi4.c

@@ -115,15 +115,6 @@ static int hdmi_init_regulator(void)
 		return PTR_ERR(reg);
 	}
 
-	if (regulator_can_change_voltage(reg)) {
-		r = regulator_set_voltage(reg, 1800000, 1800000);
-		if (r) {
-			devm_regulator_put(reg);
-			DSSWARN("can't set the regulator voltage\n");
-			return r;
-		}
-	}
-
 	hdmi.vdda_reg = reg;
 
 	return 0;

drivers/gpu/drm/omapdrm/dss/hdmi5.c

@@ -132,15 +132,6 @@ static int hdmi_init_regulator(void)
 		return PTR_ERR(reg);
 	}
 
-	if (regulator_can_change_voltage(reg)) {
-		r = regulator_set_voltage(reg, 1800000, 1800000);
-		if (r) {
-			devm_regulator_put(reg);
-			DSSWARN("can't set the regulator voltage\n");
-			return r;
-		}
-	}
-
 	hdmi.vdda_reg = reg;
 
 	return 0;