MAINTAINERS: add the PLIC interrupt controller driver to the RISC-V area

This commit adds the RISC-V Platform-Level Interrupt Controller driver to
the RISC-V area of maintenance.

Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>

MAINTAINERS.yml

@@ -2290,6 +2290,7 @@ RISCV arch:
     - soc/riscv/
     - tests/arch/riscv/
     - doc/hardware/arch/risc-v.rst
+    - drivers/interrupt_controller/intc_plic.c
   labels:
     - "area: RISCV"