PCI/DPC: Rename local "status" to "dpc_status"

In dpc_rp_pio_get_info() rename the local "status" variable to
"dpc_status".  This is to make room for another variable named "status" in
a subsequent patch.  No functional change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sinan Kaya <okaya@codeaurora.org>