mips: mt76xx: gardena-smart-gateway: Misc updates to dts/config/defconfig

mips: mt76xx: gardena-smart-gateway: Misc updates to dts/config/defconfig

These misc updates include the following changes:
- Change baudrate from 57600 to 115200
- Enable MIPS_BOOT_CMDLINE_LEGACY
- Enable FIT support
- Enable ethernet support
- Enable SPI NOR and NAND support
- Change MTD_UBI_BEB_LIMIT to 22
- Enable MTD Support
- Enable GPIO support
- Enable watchdog support
- Enable bootcounter support
- Enable version variable
- Change max image size from 0x80000 to 0xa0000
- Change SYS_MALLOC_LEN to 16MiB (because of UBI/UBIFS)

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>