mtd: rawnand: do not export nand_scan_[ident|tail]() anymore

Both nand_scan_ident() and nand_scan_tail() helpers used to be called
directly from controller drivers that needed to tweak some ECC-related
parameters before nand_scan_tail(). This separation prevented dynamic
allocations during the phase of NAND identification, which was
inconvenient.

All controller drivers have been moved to use nand_scan(), in
conjunction with the chip->ecc.[attach|detach]_chip() hooks that
actually do the required tweaking sequence between both ident/tail
calls, allowing programmers to use dynamic allocation as they need all
across the scanning sequence.

Declare nand_scan_[ident|tail]() statically now.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>