staging: dgap: Remove myself from the MAINTAINERS file

Removes myself from the MAINTAINERS file for the dgap driver.
There appears to be no way to get the firmware files required
by the dgap driver into the linux-firmware tree. The dgap
driver is useless wihtout this firmware. This product is
considered an obsolete product by Digi. They will not respond
to an inquiry concerning it or its firmware.

Signed-off-by: Mark Hounschell <markh@compro.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>