mtd: spi-nor: Off by one in cqspi_setup_flash()

There are CQSPI_MAX_CHIPSELECT elements in the ->f_pdata array so the >
should be >=.

Fixes: 140623410536 ('mtd: spi-nor: Add driver for Cadence Quad SPI Flash Controller')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
