bus: qcom-ebi2: depend on HAS_IOMEM

After being asked to not depend on ARCH_QCOM* or similar,
unsurprisingly compilation fails on UM as it has no I/O
memory:

drivers/built-in.o: In function `qcom_ebi2_probe':
>> drivers/bus/qcom-ebi2.c:333: undefined reference to
   `devm_ioremap_resource'

Fix this by letting the Kconfig atleast depend on HAS_IOMEM.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: linux-arm-msm@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>