mtd: nand: Move Samsung specific init/detection logic in nand_samsung.c

Upstream linux commit c51d0ac59f2420.

Move Samsung specific initialization and detection logic into
nand_samsung.c. This is part of the "separate vendor specific code from
core" cleanup process.

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>