mtd: spi-nor: Fix some error codes in cqspi_setup_flash()

We return success or possibly uninitialized values on these error paths
instead of proper error codes.

Fixes: 14062341 ("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>
Reviewed-by: Moritz Fischer <moritz.fischer@ettus.com>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>