USB: pxa27x_udc - Fix Oops

udc_disable oopses dereferencing udc_command.

Signed-off-by: Karl Beldan <karl.beldan@gmail.com>
Acked-by: Robert Jarzmik <rjarzmik@free.fr>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>