cupid: Configure screen density

Set the screen density according to ro.sf.lcd_density from miui.

Change-Id: Ic11b052d132f150da7070e5b8669e5a229f7528d

BoardConfig.mk

@@ -11,3 +11,6 @@ include device/xiaomi/sm8450-common/BoardConfigCommon.mk
 include vendor/xiaomi/cupid/BoardConfigVendor.mk
 
 DEVICE_PATH := device/xiaomi/cupid
+
+# Screen density
+TARGET_SCREEN_DENSITY := 440