mtd: rawnand: davinci: don't acquire and enable clock

NAND itself is an asynchronous interface, it does not have any
clock input. DaVinci NAND driver acquires clock for AEMIF
(asynchronous external memory interface) which is an on-chip
IP to which NAND is connected.

The same clock is also enabled in AEMIF driver (either present
drivers/memory or from machine code for some older platforms).
AEMIF timing must be initialized before NAND can be accessed.
This ensures that AEMIF clock is enabled too.

Remove the superfluous clock acquisition and enable in DaVinci
NAND driver.

Tested on K2L, K2HK, K2E, DA850 EVM, DA850 LCDK in device-tree
boot and DM644x EVM in legacy boot.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Tested-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>