This patch adds support to configure the AEMIF interface
with supplied timing values.

Since this capability is useful both from NOR and NAND
flashes, it is provided as a new interface and in a file
of its own.

AEMIF timing configuration is required in cases:

1) Where the AEMIF clock rate can change at runtime (a side
   affect of cpu frequency change).

2) Where U-Boot does not support NAND/NOR but supports other
   media like SPI Flash or MMC/SD and thus does not care about
   setting up the AEMIF timing for kernel to use.

3) Where U-Boot just hasn't configured the timing values and
   cannot be upgraded because the box is already in the field.

Since there is now a header file for AEMIF interface, the
common (non-NAND specific) defines for AEMIF registers have
been moved from nand.h into the newly created aemif.h
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>