xen/pt: Use XEN_PT_LOG properly to guard against compiler warnings.

If XEN_PT_LOGGING_ENABLED is enabled the XEN_PT_LOG macros start
using the first argument. Which means if within the function there
is only one user of the argument ('d') and XEN_PT_LOGGING_ENABLED
is not set, we get compiler warnings. This is not the case now
but with the "xen/pt: Use xen_host_pci_get_[byte|word] instead of dev.config"
we will hit - so this sync up the function to the rest of them.

Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>