uvk5: Fix read-only download from any firmware

This fixes the ability to download from any uvk5 in read-only mode,
regardless of firmware version. The previous patch did not properly
implement the exclusion in the download routine.

chirp/drivers/uvk5.py

@@ -545,7 +545,7 @@ def do_download(radio):
     if not f:
         raise errors.RadioError('Unable to determine firmware version')
 
-    if not radio.k5_approve_firmware(f):
+    if not radio.k5_approve_firmware(f) and radio.VARIANT != 'unsupported':
         raise errors.RadioError(
             'Firmware version is not supported by this driver')