drivers: spi: spi_max32: Handle hardware chip selection

Hardware chip select is originally handled by the HAL driver. However, a
finer grained control is needed to keep CS asserted between requests and
deassert it after last request is completed. Workaround this problem by
handling hardware chip select in Zephyr driver.

Signed-off-by: Tahsin Mutlugun <Tahsin.Mutlugun@analog.com>