mtd: Blackfin NFC: fix raw page write/read handling

mtd: Blackfin NFC: fix raw page write/read handling

Our write_buf/read_buf funcs always do ECC in HW ECC mode.  That is not
needed for raw funcs.  In fact, write_buf/read_buf should be a pure func
for data input/output while chip->ecc.hwctl controls ECC.  Unfortunately,
we can't separate ECC from normal data input/output in our NFC, so our DMA
write_buf/read_buf entries are coupled with ECC operations closely.

Thus we need to provide dedicated read_page_raw/write_page_raw funcs where
we do non-DMA transactions so as to avoid automatic ECC.

Signed-off-by: Barry Song <barry.song@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>