board: ge: bx50v3: use VPD instead of compile-time checks

B{46}50v3s have an internal LCD that needs to be configured,
in comparison with B850v3 which has only external displays.

Use VPD instead of `CONFIG_TARGET_GE_B{4,6,8}50V3' compile-time
checks to correct initialize video based on the monitor type.

Signed-off-by: Ian Ray <ian.ray@ge.com>
Signed-off-by: Nandor Han <nandor.han@ge.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

board/ge/bx50v3/bx50v3.c

@@ -366,13 +366,14 @@ int board_cfb_skip(void)
 	return 0;
 }
 
-static int detect_lcd(struct display_info_t const *dev)
+static int is_b850v3(void)
 {
-	if (IS_ENABLED(CONFIG_TARGET_GE_B450V3) ||
-	    IS_ENABLED(CONFIG_TARGET_GE_B650V3))
-		return 1;
+	return confidx == 3;
+}
 
-	return 0;
+static int detect_lcd(struct display_info_t const *dev)
+{
+	return !is_b850v3();
 }
 
 struct display_info_t const displays[] = {{
@@ -682,7 +683,7 @@ int board_early_init_f(void)
 	setup_iomux_uart();
 
 #if defined(CONFIG_VIDEO_IPUV3)
-	if (IS_ENABLED(CONFIG_TARGET_GE_B850V3))
+	if (is_b850v3())
 		/* Set LDB clock to Video PLL */
 		select_ldb_di_clock_source(MXC_PLL5_CLK);
 	else
@@ -720,7 +721,7 @@ int board_init(void)
 	gpio_direction_output(SUS_S3_OUT, 1);
 	gpio_direction_output(WIFI_EN, 1);
 #if defined(CONFIG_VIDEO_IPUV3)
-	if (IS_ENABLED(CONFIG_TARGET_GE_B850V3))
+	if (is_b850v3())
 		setup_display_b850v3();
 	else
 		setup_display_bx50v3();