mtd: nand: Move Hynix specific init/detection logic in nand_hynix.c

Upstream linux commit 01389b6bd2f4f7.

Move Hynix specific initialization and detection logic into
nand_hynix.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>