misc: keba: Use variable ret for return values

One function of the cp500 driver uses the variable name retval for
return values but all others use the variable name ret. Use ret for
return values in all functions.

Signed-off-by: Gerhard Engleder <eg@keba.com>
Link: https://lore.kernel.org/r/20241011191257.19702-2-gerhard@engleder-embedded.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>