cpqphp: Use PCI_CLASS_REVISION instead of PCI_REVISION_ID for read

While PCI_CLASS_REVISION and PCI_REVISION_ID are identical, the
code here discards the revision content and is only interested in
the class number.

Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Cc: Krosten Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>