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

This member of mite_struct is set but never used. Just remove it.

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>