staging: gasket: core: rename lookup_internal_desc to be PCI-specific

Rename lookup_internal_desc() to lookup_pci_internal_desc() to reflect
use for PCI devices only, in prep for non-PCI devices in the future.

Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>