iopsys-econet: port flags from old en7562 to en7523

Ported changes from commits:

econet: switch to new spi/spi-nand drivers
8c2aa1ef

econet: set MTD_UBI_GLUEBI=y to have an mtd emulation for ubi 'art' volume
96ab5ac5

iopsys-econet: disable ipv6 static address hook
d16e0a9c

iopsys-econet: Add loopdev and mtd_cmd to kernel
79e4b914

iopsys-econet: Enable CONFIG_GPIO_EN7523
22c0d5d5

iopsys-econet: extend dmesg buffer
76ae5cd9

iopsys-econet: pstore: Enable PSTORE support
04ce5f95

iopsys-econet: enable BRIDGE_VLAN_FILTERING flag
c9661aec

iopsys-econet: add iptables nflog module
06baedf7

iopsys-econet: Device target model build
e4a1a86d