arm: mediatek: merge board Kconfigs into mach-mediatek

On MediaTek boards we cannot override the SYS_BOARD / SYS_CONFIG_NAME
variables from defconfig.
This is because in board/mediatek/mtXXXX/Kconfig this value was override
by default due to the if CONFIG_TARGET_MTXXXX condition.

Merge all the Kconfigs to the mach-medatek/Kconfig.

This way:
- we only define SYS_{SOC,VENDOR} once
- all board definitions are in a single place, simplifying the build logic.

Signed-off-by: Guillaume La Roque <glaroque@baylibre.com>
diff --git a/arch/arm/mach-mediatek/Kconfig b/arch/arm/mach-mediatek/Kconfig
index 134b6b1..f79a5c6 100644
--- a/arch/arm/mach-mediatek/Kconfig
+++ b/arch/arm/mach-mediatek/Kconfig
@@ -79,12 +79,40 @@
 
 endchoice
 
-source "board/mediatek/mt7622/Kconfig"
-source "board/mediatek/mt7623/Kconfig"
-source "board/mediatek/mt7629/Kconfig"
-source "board/mediatek/mt8183/Kconfig"
-source "board/mediatek/mt8512/Kconfig"
-source "board/mediatek/mt8516/Kconfig"
-source "board/mediatek/mt8518/Kconfig"
+config SYS_BOARD
+	string "Board name"
+	default "mt7622" if TARGET_MT7622
+	default "mt7623" if TARGET_MT7623
+	default "mt7629" if TARGET_MT7629
+	default "mt8183" if TARGET_MT8183
+	default "mt8512" if TARGET_MT8512
+	default "mt8516" if TARGET_MT8516
+	default "mt8518" if TARGET_MT8518
+	default ""
+	help
+	  This option contains information about board name.
+	  Based on this option board/<CONFIG_SYS_VENDOR>/<CONFIG_SYS_BOARD> will
+	  be used.
+
+config SYS_CONFIG_NAME
+	string "Board configuration name"
+	default "mt7622" if TARGET_MT7622
+	default "mt7623" if TARGET_MT7623
+	default "mt7629" if TARGET_MT7629
+	default "mt8183" if TARGET_MT8183
+	default "mt8512" if TARGET_MT8512
+	default "mt8516" if TARGET_MT8516
+	default "mt8518" if TARGET_MT8518
+	default ""
+	help
+	  This option contains information about board configuration name.
+	  Based on this option include/configs/<CONFIG_SYS_CONFIG_NAME>.h header
+	  will be used for board configuration.
+
+config MTK_BROM_HEADER_INFO
+	string
+	default "media=nor" if TARGET_MT8518 || TARGET_MT8512 || TARGET_MT7629 || TARGET_MT7622
+	default "media=emmc" if TARGET_MT8516 || TARGET_MT8365 || TARGET_MT8183
+	default "lk=1" if TARGET_MT7623
 
 endif