drivers/uart: Allow the 8250IO driver only on x86

The driver relies on I/O space access functions (inb, etc.), which are
only available on x86.

Rather than explicitly disallowing it on ARM, allow it only on x86.

TEST=Configure for RISC-V, and see that "Serial port on SuperIO" is not
available in the "Generic Drivers" menu anymore.

Change-Id: Ib8e8c402264afeba6dc098683c5464af6edb3ba3
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/25631
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

0 files changed, 0 insertions, 0 deletions