[MTD] [NAND] Blackfin on-chip NAND Flash Controller driver

This is the driver for latest Blackfin on-chip nand flash controller

 - use nand_chip and mtd_info common nand driver interface
 - provide both PIO and dma operation
 - compiled with ezkit bf548 configuration
 - use hardware 1-bit ECC
 - tested with YAFFS2 and can mount YAFFS2 filesystem as rootfs

ChangeLog from try#1
 - use hweight32() instead of count_bits()
 - replace bf54x with bf5xx and BF54X with BF5XX
 - compare against plat->page_size in 2 cases when enable hardware ECC

ChangeLog from try#2
 - passed nand_test suites
 - use cpu_relax() instead of busy wait loop
 - some coding style issue pointed out by Andrew

Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>