google-crosshatch: switch to LineageOS kernel, enable /dev/mem

Tested on crosshatch.

• still boots into plasma-mobile.
• /dev/mem works. (Tested with a statically linked busybox with devmem support:)

google-crosshatch:/home/user# ./busybox devmem 0x5040000 32
0x00E01E36

• Wi-Fi still doesn't work.

I tried to boot the Wi-Fi by running echo 1 >/sys/kernel/boot_wlan/boot_wlan. This didn't help:

[  438.996345] wlan: Loading driver v5.3.1.1Q.1 ( +PANIC_ON_BUG)
[  438.996739] CHRDEV "qcwlanstate" major number 223 goes below the dynamic allocation range
[  438.997618] wlan_hdd_state wlan major(223) initialized
[  438.997621] wlan: driver loaded

then nothing more is shown. There's nothing in the firmware load log, either:

# cat /var/log/firmwareload.log 
cannot find firmware file 'venus.mdt'
(repeated 10 times)

The new device mentioned in the log is this:

# stat /dev/wlan 
  File: /dev/wlan
  Size: 0         	Blocks: 0          IO Block: 4096   character special file
Device: 6h/6d	Inode: 32392       Links: 1     Device type: df,0
Access: (0600/crw-------)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2019-01-27 04:38:22.000000000
Modify: 2019-01-27 04:38:22.000000000
Change: 2019-01-27 04:38:22.000000000

So I guess I need to run another command to further boot the Wi-Fi.

I tried the commands from main/wcnss_wlan, but that didn't help:

echo 1 > /dev/wlan
echo sta > /sys/module/wlan/parameters/fwpath

Nothing happened, no firmware loading attempt in the kernel log.

Thus, this change doesn't get Wi-Fi working, but it gives a good starting point.

This kernel takes more than one hour to build, so you might want to skip CI.

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Update google-crosshatch's kernel from the original AOSP December source to the lineage-16.0 source.

The LineageOS kernel integrates the Wi-Fi driver into the kernel source, unlike the AOSP kernel (which has it as an external module), which should help get Wi-Fi working on this device.

Also enabled /dev/mem since I thought it may be useful for dumping device registers to compare against mainline. (If you don't want this, feel free to remove this commit.)