musb_host: simplify check for active URB

The existance of the scheduling list shouldn't matter in
determining whether there's currectly an URB executing on a
hardware endpoint. What should actually matter is the 'in_qh'
or 'out_qh' fields of the 'struct musb_hw_ep' -- those are
set in musb_start_urb() and cleared in musb_giveback() when
the endpoint's URB list drains. Hence we should be able to
replace the big *switch* statements in musb_urb_dequeue()
and musb_h_disable() with mere musb_ep_get_qh() calls...

While at it, do some more changes:

 - add 'is_in' variable to musb_urb_dequeue();

 - remove the unnecessary 'epnum' variable from musb_h_disable();

 - fix the comment style in the vicinity.

This is a minor shrink of source and object code.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>