drivers: gpio: b91: add missing PLIC header

Driver is using the RISC-V PLIC interrupt controller without including
the necessary headers.

Signed-off-by: Gerard Marull-Paretas <[email protected]>

Author: gmarull

drivers/gpio/gpio_b91.c

@@ -10,6 +10,7 @@
 #include <zephyr/drivers/gpio.h>
 #include <zephyr/irq.h>
 #include <zephyr/drivers/gpio/gpio_utils.h>
+#include <zephyr/drivers/interrupt_controller/riscv_plic.h>
 
 
 /* Driver dts compatibility: telink,b91_gpio */