spi_slave_queue_reset() function

- ESP_ERR_INVALID_ARG if parameter is invalid - ESP_OK on success

This API is used to reset SPI Slave transaction queue. After calling this function: - The SPI Slave transaction queue will be reset. This API shouldn't be called when the corresponding SPI Master is doing an SPI transaction. If this gets called when its corresponding SPI Master is doing an SPI transaction, the SPI Slave behaviour is undefined