This reverts commit 4e017f14.

As explained by Rob Herring:

"This "fix" is wrong. Memory controllers with chip selects should have
the chip select in the unit-address. The correct fix here is you should drop
"simple-bus"."
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>