Disable HW inversion on rM (#6779)

Turns out it's being weird like on Mk. 7 Kobos with a crapload of PxP
processing flags.
Except without the "crapload of flags", part :D.

frontend/device/remarkable/device.lua

@@ -15,8 +15,8 @@ local Remarkable = Generic:new{
     isTouchDevice = yes,
     hasFrontlight = no,
     display_dpi = 226,
-    -- It's a recent NXP SoC, I see no reason why HW inversion would be buggy there ;).
-    canHWInvert = yes,
+    -- Despite the SoC supporting it, it's finicky in practice (#6772)
+    canHWInvert = no,
     home_dir = "/mnt/root",
 }