tests/drivers/pci_enum: move to ztest and run in HW when possible

This test case just exercises the PCI enumeration and there is no real
way to test success/failure other than running it and the kernel not
crashing.

Moved to ztest.

Retag so it is actually ran on QEMU/x86 and galileo once we deploy in
the HW pool. Note this means that we need to force CONFIG_PCI on
Qemu/x86, which can run this testcase.

Change-Id: I85b64800f7d989357927b4a25777041047293b34
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>