gpio-f7188x: switch over to using pr_fmt

gpio-f7188x: switch over to using pr_fmt

Subsequent patches will touch that file, apply some nice to have style
changes before actually adding functional changes.

Signed-off-by: Henning Schild <henning.schild@siemens.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Simon Guinot <simon.guinot@sequanux.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Bartosz Golaszewski <brgl@bgdev.pl>
Link: https://lore.kernel.org/r/20220825104422.14156-2-henning.schild@siemens.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>