This patch moves all global data structures into mv_gpio_softc,
and puts device_t parameter to functions calls everywhere where needed.
As a result, we can create multiple driver instances.
Removed names in function declaration to keep style.
Submitted by: Patryk Duda <pdk@semihalf.com>
Obtained from: Semihalf
Sponsored by: Stormshield
Differential Revision: https://reviews.freebsd.org/D14755