staging: fwserial: minor coding style fix

Fixes this checkpatch warning
WARNING: Integer promotion: Using 'h' in '%04hx' is unnecessary

Signed-off-by: Lee Gibson <leegib@gmail.com>
Link: https://lore.kernel.org/r/20210226114800.316897-1-leegib@gmail.com


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