add yaffs2 patch for hardware with nand, only use 3.14.7 for mikrotik-rb4xx for now

target/config/Config.in.kernelversion.choice

@@ -8,6 +8,7 @@ default ADK_KERNEL_VERSION_3_15_0
 
 config ADK_KERNEL_VERSION_3_15_0
 	prompt "3.15"
+	depends on !ADK_TARGET_SYSTEM_MIKROTIK_RB4XX
 	boolean
 	select ADK_KERNEL_VERSION_3_15
 
@@ -20,18 +21,21 @@ config ADK_KERNEL_VERSION_3_14_7
 config ADK_KERNEL_VERSION_3_12_22
 	prompt "3.12.22"
 	depends on !ADK_TARGET_SYSTEM_CUBOX_I
+	depends on !ADK_TARGET_SYSTEM_MIKROTIK_RB4XX
 	boolean
 	select ADK_KERNEL_VERSION_3_12
 
 config ADK_KERNEL_VERSION_3_10_43
 	prompt "3.10.43"
 	depends on !ADK_TARGET_SYSTEM_CUBOX_I
+	depends on !ADK_TARGET_SYSTEM_MIKROTIK_RB4XX
 	boolean
 	select ADK_KERNEL_VERSION_3_10
 
 config ADK_KERNEL_VERSION_3_10_30
 	prompt "3.10.30"
 	depends on ADK_TARGET_SYSTEM_CUBOX_I
+	depends on !ADK_TARGET_SYSTEM_MIKROTIK_RB4XX
 	boolean
 	select ADK_KERNEL_VERSION_3_10
 
@@ -39,6 +43,7 @@ config ADK_KERNEL_VERSION_3_4_93
 	prompt "3.4.93"
 	depends on !ADK_TARGET_SYSTEM_RASPBERRY_PI
 	depends on !ADK_TARGET_SYSTEM_CUBOX_I
+	depends on !ADK_TARGET_SYSTEM_MIKROTIK_RB4XX
 	boolean
 	select ADK_KERNEL_VERSION_3_4
 

target/linux/config/Config.in.addons

@@ -2,6 +2,7 @@
 # material, please see the LICENCE file in the top-level directory.
 
 config ADK_KERNEL_ADDON_YAFFS2
+	default y if ADK_TARGET_WITH_NAND
 	boolean
 
 config ADK_KERNEL_ADDON_GRSEC