Add support for FrSky OSD

- Add displayWriteFontCharacter() for font writing, removing all max7456
specific code.
- Add displayIsReady() for asynchronous display initialization
- Add displayBeginTransaction()/displayCommitTransaction() for display
transactions, which allow performing complex drawing operations without
flickering
- Add displayGetCanvas(), which retrieves the canvas associated with a
display (if it has it)
- Add canvas implementation for pixel based access for a display
- Add FrSkyOSD driver and displayPort driver
- Enable FrSkyOSD driver for targets with flash > 256
- Rename max7456_symbols.h to osd_symbols.h

src/main/cli/cli.c

@@ -1253,8 +1253,8 @@ static void cliSerial(char *cmdline)
 
     ptr = nextArg(ptr);
     if (ptr) {
-        val = atoi(ptr);
-        portConfig.functionMask = val & 0xFFFF;
+        val = strtoul(ptr, NULL, 10);
+        portConfig.functionMask = val;
         validArgumentCount++;
     }