staging: comedi: mite: remove mite_struct member 'daq_phys_addr'

This member of mite_struct is only used to map the mite I/O window.
For aesthetics, remove it and use a local variable instead.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>