gpio: make memory-mapped drivers depend on HAS_IOMEM

This one is pretty obvious: on UM Linux compilation of things
like allmodconfig and allyesconfig will fail due to the
absence of IO memory. Simply make these drivers depend on
HAS_IOMEM, it has been implicitly assumed all the time, so
just make it explicit.

The generic MMIO library also assumes that IOMEM is present
so make also this depend on HAS_IOMEM.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>