musb_hdrc: Fix musb_hnp_stop() to return to device mode

This one fixes some USB HS OPT test unreliability.

Tony

From: Tony Lindgren <tony@atomide.com>
Subject: musb_hdrc: Fix musb_hnp_stop() to return to device mode

Without this patch HNP does not return to device mode, which can
confuse OPT tests. Also change to b_host if SUSPEND and CONNECT
simultaneously as b_peripheral, and fix a comment.

Signed-off-by: Tony Lindgren <tony@atomide.com>