lib: utils/ipi: Add Andes fdt ipi driver support

Move Andes PLICSW ipi device to fdt ipi framework, this patch is based
on Leo's modified IPI scheme on PLICSW.

Current IPI scheme uses bit 0 of pending reigster on PLICSW to send IPI
from hart 0 to hart 7, but bit 0 needs to be hardwired to 0 according
to spec. After some investigation, self-IPI seems to be seldom or never
used, so we re-order the IPI scheme to support 8 core platforms.

dts example (Quad-core AX45MP):

  plicsw: interrupt-controller@e6400000 {
          compatible = "andestech,plicsw";
          reg = <0x00000000 0xe6400000 0x00000000 0x00400000>;
          interrupts-extended = <&CPU0_intc 3
                                 &CPU1_intc 3
                                 &CPU2_intc 3
                                 &CPU3_intc 3>;
          interrupt-controller;
          #address-cells = <2>;
          #interrupt-cells = <2>;
  };

Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>