lpc3180: LPC3180(LPC3250) SLC driver implemented

lpc3180: LPC3180(LPC3250) SLC driver implemented

Until this time only basic  SLC functionality exists when you want to use SLC to access external nand flash.
Basic functionality can be selected with command:
     lpc3180 select 0 slc
It is anyway very slow to write/read to/from nand flash.

With the new command, SLC speed improved about 20 times, and hardware ECC info also read/written from/to nand flash OOB area:
     lpc3180 select 0 slc bulk
Speed improvement achieved by using working are in SRAM of the LPC3250 chip and controlling DMA controller to interact between SRAM and SLC peripheral.

Here are the patches, and if they are ok than take them.
Tested with hitex LPC3250 usb stick.

Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>