usb: dwc2: Fix build in periphal-only mode

In branches to which 24d209dba5a3 ("usb: dwc2: Fix hibernation between
host and device modes.") has been back-ported, the bus_suspended member
of struct dwc2_hsotg is only present in builds that support host-mode.
To avoid having to pull in several more non-Fix commits in order to
get it to compile, wrap the usage of the member in a macro conditional.

Fixes: 24d209dba5a3 ("usb: dwc2: Fix hibernation between host and device modes.")
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>