intel: n5x: ddr: update license

All the source code of sdram_n5x.c are from Intel, update the license to
use both GPL2.0 and BSD-3 Clause because this copy of code may used for
open source and internal project.

Signed-off-by: Tien Fong Chee <tien.fong.chee@intel.com>
1 file changed