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/mips/mach-mtmips/Kconfig b/arch/mips/mach-mtmips/Kconfig
index 9f300a9..151b004 100644
--- a/arch/mips/mach-mtmips/Kconfig
+++ b/arch/mips/mach-mtmips/Kconfig
@@ -1,6 +1,9 @@
 menu "MediaTek MIPS platforms"
 	depends on ARCH_MTMIPS
 
+config SYS_VENDOR
+	default "mediatek" if BOARD_MT7628_RFB || BOARD_MT7620_RFB || BOARD_MT7620_MT7530_RFB
+
 config SYS_MALLOC_F_LEN
 	default 0x1000
 
diff --git a/arch/mips/mach-mtmips/mt7620/Kconfig b/arch/mips/mach-mtmips/mt7620/Kconfig
index 5db83eb..3ca711a 100644
--- a/arch/mips/mach-mtmips/mt7620/Kconfig
+++ b/arch/mips/mach-mtmips/mt7620/Kconfig
@@ -66,6 +66,12 @@
 	default 6 if CPU_FREQ_600MHZ
 	default 7 if CPU_FREQ_620MHZ
 
-source "board/mediatek/mt7620/Kconfig"
+config SYS_CONFIG_NAME
+	string "Board configuration name"
+	default "mt7620" if  BOARD_MT7620_RFB || BOARD_MT7620_MT7530_RFB
+
+config SYS_BOARD
+	string "Board name"
+	default "mt7620" if  BOARD_MT7620_RFB || BOARD_MT7620_MT7530_RFB
 
 endif
diff --git a/arch/mips/mach-mtmips/mt7628/Kconfig b/arch/mips/mach-mtmips/mt7628/Kconfig
index f451c15..e727359 100644
--- a/arch/mips/mach-mtmips/mt7628/Kconfig
+++ b/arch/mips/mach-mtmips/mt7628/Kconfig
@@ -44,8 +44,15 @@
 	  Select this if the UART2 of your board is connected to GPIO 16/17
 	  (shared with SPIS) rather than the usual GPIO 20/21.
 
+config SYS_BOARD
+	string "Board name"
+	default "mt7628" if BOARD_MT7628_RFB
+
+config SYS_CONFIG_NAME
+	string "Board configuration name"
+	default "mt7628" if BOARD_MT7628_RFB
+
 source "board/gardena/smart-gateway-mt7688/Kconfig"
-source "board/mediatek/mt7628/Kconfig"
 source "board/seeed/linkit-smart-7688/Kconfig"
 source "board/vocore/vocore2/Kconfig"