mtd: rawnand: qcom: Rename variables in qcom_op_cmd_mapping()

qcom_op_cmd_mapping() function accepts opcode and returns the corresponding
command register. So let's rename the local variables and parameters to
reflect the same.

Reported-by: Miquel Raynal <miquel.raynal@bootlin.com>
Closes: https://lore.kernel.org/all/20230804190750.3367a044@xps-13/
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230805174146.57006-3-manivannan.sadhasivam@linaro.org