usb: host: fix incorrect updating of offset

commit 1d5a31582ef046d3b233f0da1a68ae26519b2f0a upstream.

The variable temp is incorrectly being updated, instead it should
be offset otherwise the loop just reads the same capability value
and loops forever.  Thanks to Alan Stern for pointing out the
correct fix to my original fix.  Fix also cleans up clang warning:

drivers/usb/host/ehci-dbg.c:840:4: warning: Value stored to 'temp'
is never read

Fixes: d49d4317 ("USB: misc ehci updates")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>