driver core: Export get_dev_from_fwnode()

It has turned out get_dev_from_fwnode() is useful at a few other places
outside of the driver core, as in gpiolib.c for example. Therefore let's
make it available as a common helper function.

Suggested-by: Saravana Kannan <saravanak@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: Hiago De Franco <hiago.franco@toradex.com> # Colibri iMX8X
Tested-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> # TI AM62A,Xilinx ZynqMP ZCU106
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20250701114733.636510-18-ulf.hansson@linaro.org