Add support for Mikrotik LHGG (RBLHGGR)

Product Page RBLHGGR&R11e-LTE6
Hello, was wonderind if it's possible to adds this nice CPE on Openwrt.
it have Marvell® ARMADA 88F3720 SoC, which is already supported, and nothing else.
It just have 1 ethernet port PoE and 1 minipcie for 4g/5g, really nice outdoor cpe to be used for LTE/5g modems you can bridge to an internal router for optimal connection.

Architecture ARM 64bit
CPU 88F3720
CPU core count 2
CPU nominal frequency 800 MHz
Size of RAM 256 MB
Storage size 16 MB
Storage type FLASH