reMarkable: add environment variable to tell koreader.sh to not set bpp (#6685)

* reMarkable: add environment variable to tell koreader.sh to not set bpp

platform/remarkable/koreader.sh

@@ -96,6 +96,10 @@ esac
 
 # The actual swap is done in a function, because we can disable it in the Developer settings, and we want to honor it on restart.
 ko_do_fbdepth() {
+    if [ -n "${KO_DONT_SET_DEPTH}" ]; then
+        return
+    fi
+
     # Check if the swap has been disabled...
     if grep -q '\["dev_startup_no_fbdepth"\] = true' 'settings.reader.lua' 2>/dev/null; then
         # Swap back to the original bitdepth (in case this was a restart)