USB: musb_gadget_ep0: stop abusing musb_gadget_set_halt()

Stop playing with musb->lock and abusing musb_gadget_set_halt() in
the code clearing the endpoint halt feature -- instead, manipulate
the registers directly.

While at it, get rid uf unneeded line breaks and over-indentation in
the code setting the endpoint halt feature.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>