usb: musb: gadget: only enable AUTOCLEAR in double buffered case

commit 633ba7876b96ec339ef685357e2f7c60b5a8ce85 broke
g_file_storage functionality by enabling AUTOCLEAR on
all cases without caring for all gadget drivers.

This patch will only enable AUTOCLEAR if our endpoint's
FIFO was configured with double buffering support. Note
this is not a complete fix, double buffered case still
doesn't work always, but that hasn't been working for
quite some time. Other than reverting the entire commit
and breaking testusb with double buffered case again,
I decided it was better to fix the single buffered case
and spend more time fixing double buffered case properly.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>