generic: platform/mikrotik: add wlan lz77 decompress

generic: platform/mikrotik: add wlan lz77 decompress

A number of new (or with recently updated caldata)
Mikrotik devices are using LZ77 magic for wlan tag hard_config data.
New devices include the Chateau LTE12 [1], and ax devices [2]
Newly factory flashed devices may include the hap ac3 [3]

This can be seen in decoded OEM supout [4] dmesg:
"radio data lz77 decompressed from"…

Investigating an arm RouterOS flash.ko module, and supplied example
hard_config dumps, the format was guessed via decompilation and live
debugging [5]. This decoder was then built from the guessed format
specification.

debug prints can be enabled in a DYNAMIC_DEBUG kernel build via the
kernel cmdline:

        chosen {
-               bootargs = "console=ttyS0,115200";
+               bootargs = "console=ttyS0,115200 dyndbg=\"file drivers/platform/mikrotik/* +p\"";
        };

[1]: https://forum.openwrt.org/t/no-wireless-mikrotik-rbd53ig-5hacd2hnd/157763/4
[2]: https://forum.openwrt.org/t/mikrotik-routeros-v7-x-and-openwrt-sysupgrade/148072/17
[3]: https://forum.openwrt.org/t/adding-support-for-mikrotik-hap-ax2/133715/47
[4]: https://github.com/farseeker/go-mikrotik-rif
[5]: https://github.com/john-tho/routeros-wlan-lz77-decode

Signed-off-by: John Thomson <git@johnthomson.fastmail.com.au>
Link: https://github.com/openwrt/openwrt/pull/15774
Signed-off-by: Robert Marko <robimarko@gmail.com>