[spi_host] Option to manually control spi_host chip select

### Description

Hello,

In the current implementation, the spi_host IP automatically controls the chip select (CS) signal when transmitting or receiving data.

I would like to know if there is a way to:

1. Disable or override the automatic CS behavior.
2. Control the chip select manually using a GPIO.
3. Replace the CS signal from spi_host with a GPIO-driven signal.

Is there an existing configuration option for this, or would this require modifying the design? Any guidance or documentation reference would be greatly appreciated.

Start with the spi_host IP implementation and its available configuration or documentation, then trace how chip select is connected and controlled during transfers. Confirm whether manual GPIO control is already supported; done should be a documented answer or a clearly scoped design change covering disabled, overridden, and GPIO-driven CS behavior.

Written by the indexing model from the issue text.