net: gemini: Depend on HAS_IOMEM

The zeroday builder notices that since Usermode Linux does not
have IO memory, the build fails for them when selecting everything
it can enable.

As the driver is clearly using memory-mapped registers to access
the network adapter, we add depends on HAS_IOMEM to solve this
problem.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>