drivers/ddr/fsl: Dual-license DDR driver

To make this driver easier to be reused, dual-license DDR driver.

Signed-off-by: York Sun <york.sun@nxp.com>
CC: Simon Glass <sjg@chromium.org>
CC: Tom Rini <trini@konsulko.com>
CC: Heinrich Schuchardt <xypron.glpk@gmx.de>
CC: Thomas Schaefer <thomas.schaefer@kontron.com>
CC: Masahiro Yamada <yamada.masahiro@socionext.com>
CC: Robert P. J. Day <rpjday@crashcourse.ca>
CC: Alexander Merkle <alexander.merkle@lauterbach.com>
CC: Joakim Tjernlund <joakim.tjernlund@transmode.se>
CC: Curt Brune <curt@cumulusnetworks.com>
CC: Valentin Longchamp <valentin.longchamp@keymile.com>
CC: Wolfgang Denk <wd@denx.de>
CC: Anatolij Gustschin <agust@denx.de>
CC: Ira W. Snyder <iws@ovro.caltech.edu>
CC: Marek Vasut <marek.vasut@gmail.com>
CC: Kyle Moffett <Kyle.D.Moffett@boeing.com>
CC: Sebastien Carlier <sebastien.carlier@gmail.com>
CC: Stefan Roese <sr@denx.de>
CC: Peter Tyser <ptyser@xes-inc.com>
CC: Paul Gortmaker <paul.gortmaker@windriver.com>
CC: Peter Tyser <ptyser@xes-inc.com>
CC: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>