dt-bindings: timer: Add SiFive CLINT2

Add compatible string and property for the SiFive CLINT v2. The SiFive
CLINT v2 is incompatible with the SiFive CLINT v0 due to differences
in their control methods.

Signed-off-by: Nick Hu <[e-mail]>
Reviewed-by: Samuel Holland <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Daniel Lezcano <[e-mail]>

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

···
               - starfive,jh8100-clint   # StarFive JH8100
           - const: sifive,clint0        # SiFive CLINT v0 IP block
       - items:
+          - {}
+          - const: sifive,clint2        # SiFive CLINT v2 IP block
+        description:
+          SiFive CLINT v2 is the HRT that supports the Zicntr. The control of sifive,clint2
+          differs from that of sifive,clint0, making them incompatible.
+      - items:
           - enum:
               - allwinner,sun20i-d1-clint
               - sophgo,cv1800b-clint
···
   interrupts-extended:
     minItems: 1
     maxItems: 4095
+
+  sifive,fine-ctr-bits:
+    maximum: 15
+    description: The width in bits of the fine counter.
+
+if:
+  properties:
+    compatible:
+      contains:
+        const: sifive,clint2
+then:
+  required:
+    - sifive,fine-ctr-bits
+else:
+  properties:
+    sifive,fine-ctr-bits: false
 
 additionalProperties: false