dm: MIGRATION: Add migration plan for CONFIG_SATA

As the core of the subsystem has been converted along with some of the
drivers, formalize a deadline for migration.

Cc: Akshay Bhat <akshaybhat@timesys.com>
Cc: Andreas Geisreiter <ageisreiter@dh-electronics.de>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Jason Liu <jason.hui.liu@nxp.com>
Cc: Ken Lin <Ken.Lin@advantech.com.tw>
Cc: Ludwig Zenz <lzenz@dh-electronics.de>
Cc: Marek Vasut <marex@denx.de>
Cc: Max Krummenacher <max.krummenacher@toradex.com>
Cc: Nikita Kiryanov <nikita@compulab.co.il>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Cc: Soeren Moch <smoch@web.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Tim Harvey <tharvey@gateworks.com>
Cc: Troy Kisky <troy.kisky@boundarydevices.com>
Cc: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Cc: York Sun <york.sun@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>