usb: host: unhide suspend/resume declarations

There is no need to hide function declarations, and making
these visible to the SoC specific host drivers lets us
use __maybe_unused and IS_ENABLED() checks to control
their use, rather than having to use #ifdef to hide all
callers.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>