mtd: spi-nor: cadence-quadspi: Make driver independent of flash geometry

Drop configuration of Flash size, erase size and page size
configuration. Flash size is needed only if using AHB decoder (BIT 23 of
CONFIG_REG) which is not used by the driver.
Erase size and page size are needed if IP is configured to send WREN
automatically. But since SPI NOR layer takes care of sending WREN, there
is no need to configure these fields either.

Therefore drop these in preparation to move the driver to spi-mem
framework where flash geometry is not visible to controller driver.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>