USB: xhci: Print NEC firmware version.

The NEC xHCI host controller firmware version can be found by putting a
vendor-specific command on the command ring and extracting the BCD
encoded-version out of the vendor-specific event TRB.

The firmware version debug line in dmesg will look like:

xhci_hcd 0000:05:00.0: NEC firmware version 30.21

(NEC merged with Renesas Technologies and became Renesas Electronics on
April 1, 2010.  I have their OK to merge this vendor-specific code.)

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Satoshi Otani <satoshi.otani.xm@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>