drivers: sdhc: fix infineon cat1 gpio initialization

Initialize the cyhal_sdio_config, such that the init
function won't do the pin configuration.
The gpios are setup using the zephyr pinctrl driver already.

Before the latest hal update the values were ignored and
the gpio configuration completely skipped.
But this is no longer the case and this commit
fixes that by setting the gpio pins to nc,

Also, explicitly set sdio_config.clock to NULL, to make
it clearer that the driver will check for that.

Signed-off-by: Thomas Stranger <thomas.stranger@outlook.com>