soc: esp32: riscv: fix interrupt allocator

Current interrupt allocator is not taking into account
reserved areas. In case of esp32c6, Wi-Fi isn't properly
configured, causing instability or even non-functional feature.
This adds the reserved area ranges for all risc-v based SoC and
unify the slot finding based on interrupt source.

Signed-off-by: Sylvio Alves <sylvio.alves@espressif.com>