Convert CONFIG_AT91SAM9G20EK et al to Kconfig

This converts the following to Kconfig:
   CONFIG_AT91SAM9G20EK
   CONFIG_AT91SAM9260EK
   CONFIG_AT91SAM9G20EK_2MMC

Cc: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/at91sam9g20ek_2mmc_nandflash_defconfig b/configs/at91sam9g20ek_2mmc_nandflash_defconfig
index b2ee395..37a420e 100644
--- a/configs/at91sam9g20ek_2mmc_nandflash_defconfig
+++ b/configs/at91sam9g20ek_2mmc_nandflash_defconfig
@@ -6,6 +6,8 @@
 CONFIG_SYS_MALLOC_LEN=0x80000
 CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_TARGET_AT91SAM9260EK=y
+CONFIG_AT91SAM9260EK=y
+CONFIG_AT91SAM9G20EK_2MMC=y
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_DM_GPIO=y
 CONFIG_DEFAULT_DEVICE_TREE="at91sam9g20ek_2mmc"
@@ -15,7 +17,7 @@
 CONFIG_ENV_OFFSET_REDUND=0x100000
 CONFIG_DEBUG_UART=y
 CONFIG_SYS_LOAD_ADDR=0x22000000
-CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9G20EK_2MMC,SYS_USE_NANDFLASH"
+CONFIG_SYS_EXTRA_OPTIONS="SYS_USE_NANDFLASH"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 earlyprintk mtdparts=atmel_nand:256k(bootstrap)ro,512k(uboot)ro,256k(env),256k(env_redundant),256k(spare),512k(dtb),6M(kernel)ro,-(rootfs) root=/dev/mtdblock7 rw rootfstype=jffs2"