drivers: intc_plic: fix plic PLIC_TRIG_LEVEL define mistake

Interrupt trigger type register each bit indicate the configured interrupt
type. bit value is 0 indicate level trigger interrupt, 1 indicate edge
trigger interrupt.

The level trigger defined to ~BIT(0) equal 0xfffffffe not equal 0.

Signed-off-by: Weiwei Guo <guoweiwei@syriusrobotics.com>