According to Armada 8k documentation, the interrupt cause register
(at offset 0x14) is RW0C. Update the configuration in attach and
the mvebu_gpio_isrc_eoi() to follow the description.
Reviewed by: mmel
Obtained from: Semihalf
Sponsored by: Marvell
Differential Revision: https://reviews.freebsd.org/D29013
Module name (unlike of the of driver name) must be system wide unique.
Reported by: Mark Millard(bcm_pci), andrew(mvebu_gpio)
MFC with: r362954, r362385