staging: kpc2000: Add DMA driver

Add Daktronics DMA driver.  I've added the SPDX license identifiers, Kconfig
entry, and cleaned up as many of the warnings as I could.

The AIO support code will be removed in a future patch.

Signed-off-by: Matt Sickler <matt.sickler@daktronics.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>