drivers: interrupt_controller: esp32c6: reserve IRQ 1 for WiFi

IRQ 1 is reserved for WiFi in ESP-IDF, which is used as the basis
for the Espressif HAL in Zephyr.

If IRQ 1 is used by Zephyr and too many other peripherals (e.g.
multiple UARTs) are enabled, WiFi stops working.

Marking IRQ 1 as "not available" seems to fix the issue.

Fixes #82874

Signed-off-by: Martin Jäger <martin@libre.solar>