ath79: enable NVMEM u-boot-env driver on generic subtarget

This patch enables NVMEM u-boot-env driver (COFNIG_NVMEM_U_BOOT_ENV) on
generic subtarget to use from devices, for MAC address and etc.

Signed-off-by: INAGAKI Hiroshi <[email protected]>

target/linux/ath79/generic/config-default

@@ -15,6 +15,8 @@ CONFIG_MARVELL_PHY=y
 CONFIG_MICREL_PHY=y
 CONFIG_MTD_REDBOOT_PARTS=y
 CONFIG_MTD_SPLIT_EVA_FW=y
+CONFIG_NVMEM_SYSFS=y
+CONFIG_NVMEM_U_BOOT_ENV=y
 CONFIG_PHY_AR7100_USB=y
 CONFIG_PHY_AR7200_USB=y
 CONFIG_REALTEK_PHY=y