usb:xhci:Fix regression when ATI chipsets detected

usb:xhci:Fix regression when ATI chipsets detected

BugLink: http://bugs.launchpad.net/bugs/1716284
commit e6b422b88b46353cf596e0db6dc0e39d50d90d6e upstream.

The following commit cause a regression on ATI chipsets.
'commit e788787ef4f9 ("usb:xhci:Add quirk for Certain
failing HP keyboard on reset after resume")'

This causes pinfo->smbus_dev to be wrongly set to NULL on
systems with the ATI chipset that this function checks for first.

Added conditional check for AMD chipsets to avoid the overwriting
pinfo->smbus_dev.

Reported-by: Ben Hutchings <ben@decadent.org.uk>
Fixes: e788787ef4f9 ("usb:xhci:Add quirk for Certain
failing HP keyboard on reset after resume")
cc: Nehal Shah <Nehal-bakulchandra.Shah@amd.com>
Signed-off-by: Sandeep Singh <Sandeep.Singh@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>