cfi: Add support for strangely endianness broken SoC implementations

cfi: Add support for strangely endianness broken SoC implementations

This adds the 'data_swap' parameter to the CFI driver, which enables
swapping of data bytes when writing/programming words to the flash.
Note, that this specifically means that bytes are not swapped when
writing command words to the flash chip.  Unless you are using the SAP
in an LS102x chip to program an attached 16-bit NOR flash, you hopefully
do not need this!

Change-Id: I1e6f7169da36f373c880d1756d9c21c9957acc50
Signed-off-by: Esben Haabendal <esben@haabendal.dk>
Reviewed-on: http://openocd.zylin.com/3109
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>