[PATCH] shpchp: detect SHPC capability before doing a lot of work

The shpc driver registers its probe function for all pci-pci
bridges in the system. Not all of them will be shpc capable, so
look for this capability early in the probe function and return
if there's no work to do on this bridge. The old shpc driver
did some initialization work on all bridges before detecting
that shpc is not supported and unwinds the work it's already done
in that case.

Signed-off-by: Rajesh Shah <rajesh.shah@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>