PCI: vmd: depend on !UML

With UML having enabled (simulated) PCI on UML, VMD breaks
allyesconfig/allmodconfig compilation because it assumes
it's running on X86_64 bare metal, and has hardcoded API
use of ARCH=x86. Make it depend on !UML to fix this.

Link: https://lore.kernel.org/r/20210811162530.affe26231bc3.I131b3c1e67e3d2ead6e98addd256c835fbef9a3e@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Jon Derrick <jonathan.derrick@intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested