KOReader: Disable HW inversion in case it's unreliable (e.g., mxcfb on old ntx kernels).

2-disable-hw-invert.lua

local Device = require("device")
local Screen = Device.screen

-- Flipping canHWInvert affects what fb:toggleNightmode does, so make sure we flip it with NM *off*, 
-- because it'll already have been run by Device:init before this patch runs...
-- Otherwise we'll flip the Screen's bb invert flag the wrong way around ;).
local is_nm = Screen.night_mode
if is_nm then
	Screen:toggleNightMode()
end

Device.canHWInvert = function() return false end

if is_nm then
	Screen:toggleNightMode()
end

how do I apply this patch?

c.f., https://github.com/koreader/koreader/wiki/User-patches

done that

Updated to fix the breakage when restarting with nightmode enabled ;).