i2c: scx200_acb: depends on HAS_IOPORT

It already depends on X86_32, but that's also set for ARCH=um.
Recent changes made UML no longer have IO port access since
it's not needed, but this driver uses it. Build it only for
HAS_IOPORT. This is pretty much the same as depending on X86,
but on the off-chance that HAS_IOPORT will ever be optional
on x86 HAS_IOPORT is the real prerequisite.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>