Staging: mrst-touchscreen: Fix wrong Makefile config

The config name is wrong in drivers/staging/Makefile...
The object name is wrong in drivers/staging/mrst-touchscreen/Makefile...

Signed-off-by: Alek Du <alek.du@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>