arm64: QorIQ: gpio: Cleanup qoriq_gpio_* helpers

Replace various hw reg bit set/clear helpers with a universal
qoriq_gpio_set function.

Submitted by: Artur Rojek <ar@semihalf.com>
Reviewed by: mmel
Obtained from: Semihalf
Sponsored by: Alstom Group
Differential Revision: https://reviews.freebsd.org/D26868