Staging: sst: Construct fw string name runtime

The firmware name for each platform is appended by PCI id of device.
This patch makes use of pci id to construct the string rather than
hardcode the string.

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>