ath79: tiny: enable NVMEM u-boot-env driver

The upcoming D-Link devices to the tiny sub-target require it to
parse the u-env MAC address. The kernel size will increase by
about 1 KiB.

Signed-off-by: Shiji Yang <[email protected]>

target/linux/ath79/tiny/config-default

@@ -6,6 +6,8 @@ CONFIG_NET_DSA=y
 CONFIG_NET_DSA_MV88E6060=y
 CONFIG_NET_DSA_TAG_TRAILER=y
 CONFIG_NET_SWITCHDEV=y
+CONFIG_NVMEM_SYSFS=y
+CONFIG_NVMEM_U_BOOT_ENV=y
 CONFIG_PHYLINK=y
 CONFIG_PHY_AR7100_USB=y
 CONFIG_PHY_AR7200_USB=y