usb: musb: da8xx: Remove try_idle implementation from host-only mode

usb: musb: da8xx: Remove try_idle implementation from host-only mode

The idle_state is not meant for host-only mode. When the device acts as a
host, it fails to exit the idle state once entered. This prevents new
USB gadgets from being detected once plugged in.

Commit 032ec49f5351 ("usb: musb: drop useless board_mode usage") removed
a is_otg_enabled() check in the try_idle() that prevented from entering
idle_state. This was removed because at that time it was not possible to
select host-only mode with CONFIG_USB_MUSB_HOST so dual role was always
set.

Add #ifndef CONFIG_USB_MUSB_HOST around try_idle() callback to prevent
from entering idle_state when host-only mode has been selected.

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
Link: https://lore.kernel.org/r/20240528102026.40136-4-bastien.curutchet@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>