mtd: rawnand: arasan: Update NAND bus clock instead of system clock

In current implementation the Arasan NAND driver is updating the
system clock(i.e., anand->clk) in accordance to the timing modes
(i.e., SDR or NVDDR). But as per the Arasan NAND controller spec the
flash clock or the NAND bus clock(i.e., nfc->bus_clk), need to be
updated instead. This patch keeps the system clock unchanged and updates
the NAND bus clock as per the timing modes.

Fixes: 197b88fe ("mtd: rawnand: arasan: Add new Arasan NAND controller")
CC: stable@vger.kernel.org # 5.8+
Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@xilinx.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220628154824.12222-2-amit.kumar-mahapatra@xilinx.com