ARM: davinci: aemif: get rid of davinci-nand driver dependency on aemif

The problem that the set timings code contains the call of Davinci
platform function davinci_aemif_setup_timing() which is not
accessible if kernel is built for another platform like Keystone.

The Keysone platform is going to use TI AEMIF driver.
If TI AEMIF is used we don't need to set timings and bus width.
It is done by AEMIF driver.

To get rid of davinci-nand driver dependency on aemif platform code
we moved aemif code to davinci platform.

The platform AEMIF code (aemif.c) has to be removed once Davinci
will be converted to DT and use ti-aemif.c driver.

Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
[nsekhar@ti.com: fixed checkpatch error and a build breakage due to
		 missing include, rebased onto l2-mtd/master]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>