dt-bindings: timer: sifive,clint: add pic64gx compatibility

As mention in sifive,clint.yaml, a specific compatible should be used
for pic64gx, so here it is.

Signed-off-by: Pierre-Henry Moussay <pierre-henry.moussay@microchip.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

Author: Pierre-Henry Moussay

Documentation/devicetree/bindings/timer/sifive,clint.yaml

@@ -31,6 +31,7 @@ properties:
           - enum:
               - canaan,k210-clint       # Canaan Kendryte K210
               - eswin,eic7700-clint     # ESWIN EIC7700
+              - microchip,pic64gx-clint # Microchip PIC64GX
               - sifive,fu540-c000-clint # SiFive FU540
               - spacemit,k1-clint       # SpacemiT K1
               - spacemit,k3-clint       # SpacemiT K3