dt-bindings: riscv: add Zvfh[min] ISA extension description

Add description for Zvfh[min] ISA extension[1].

Link: https://drive.google.com/file/d/1_Yt60HGAf1r1hx7JnsIptw0sqkBd9BQ8/view [1]
Signed-off-by: Clément Léger <cleger@rivosinc.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231114141256.126749-18-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Documentation/devicetree/bindings/riscv/extensions.yaml

@@ -369,6 +369,18 @@ properties:
             instructions, as ratified in commit 56ed795 ("Update
             riscv-crypto-spec-vector.adoc") of riscv-crypto.
 
+        - const: zvfh
+          description:
+            The standard Zvfh extension for vectored half-precision
+            floating-point instructions, as ratified in commit e2ccd05
+            ("Remove draft warnings from Zvfh[min]") of riscv-v-spec.
+
+        - const: zvfhmin
+          description:
+            The standard Zvfhmin extension for vectored minimal half-precision
+            floating-point instructions, as ratified in commit e2ccd05
+            ("Remove draft warnings from Zvfh[min]") of riscv-v-spec.
+
         - const: zvkb
           description:
             The standard Zvkb extension for vector cryptography bit-manipulation