mtd: nand: fsmc: remove fsmc_select_chip()

host->select_chip used to point to the ->select_bank() function provided
by the platform data, but the latter no longer exists. Therefore
host->select_chip is always NULL.

Due to this, the fsmc_select_chip() does nothing, except:

  chip->cmd_ctrl(mtd, NAND_CMD_NONE, 0 | NAND_CTRL_CHANGE);

when chipnr is -1, which is exactly what the default implementation of
->select_chip() does in the NAND framework. So, this commit kills
fsmc_select_chip() entirely.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>