Adding OpenWrt support for Xiaomi AX3600 (Part 1)

[perceival]

Managed to brick my AX3600. Would appreciate any ideas.
Boot process stops at:

B -    441426 - Error code 1000001 at boot_config.c Line 280

AX3600 turned into solid brick

After a few months of playing with Xiaomi AX3600 I managed to break it beyond my unbricking skills. Following mistakenly restored incorrect config backup it produces only that: Format: Log Type - Time(microsec) - Message - Optional Info Log Type: B - Since Boot(Power On Reset), D - Delta, S - Statistic S - QC_IMAGE_VERSION_STRING=BOOT.BF.3.3.1-00147 S - IMAGE_VARIANT_STRING=HAACANAZA S - OEM_IMAGE_VERSION_STRING=CRM S - Boot Config, 0x000002e5 B - 201 - PBL, Start B - 2735 - bootab…