pci(4): unbreak the build

argsp is not defined in generic_pcie_unmap_resource(..). Remove the
parameter passed to bus_generic_unmap_resource(..) as this parameter
is never passed to generic_pcie_unmap_resource(..).

Fixes: 98056127ddfa ("acpi/pci/vmd: Fix a nit with nested resource mapping requests")
Reported by: Jenkins (aarch64, armv6, armv7, etc)
Differential Revision: https://reviews.freebsd.org/D45493