memory: ti-aemif: Add DM support

memory: ti-aemif: Add DM support

The AEMIF's bindings in the Linux tree have a node for the AEMIF
controller and then a node for each AEMIF's chip select. This CS node
doesn't have a compatible property but describes the timing parameters
used by a given chip select.
The U-Boot DM framework expects every node to have a 'compatible'
property. If no 'compatible' is present in a node, its children won't be
parsed by u-boot.

Add DM support to the ti-aemif driver.
Add a new ti-aemif-cs driver to comply with the Linux bindings and the
U-Boot's DM philosophy. This driver handles the timing parameters
of an AEMIF's chip select so move aemif_cs_configure() from ti-aemif.c
to ti-aemif-cs.c.

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>