The traditional IO Port configuration mechanism was technically
deprecated about 15 years ago when PCI Express started shipping.
While frankly the MMIO support is significantly more complicated and
no more performant in practice, Zephyr should have support for current
standards. And (particularly complicated) devices do exist in the
wild whose extended capability pointers spill beyond the 256 byte area
allowed by the legacy mechanism. Zephyr will want drivers for those
some day.
Also, Windows and Linux use MMIO access, which means that's what
system vendors validate.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>