dt-bindings: pwm: Update DT binding docs to support SiFive FU740 SoC

Add new compatible strings to the DT binding documents to support SiFive
FU740-C000.
Signed-off-by: Yash Shah <yash.shah@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

Documentation/devicetree/bindings/pwm/pwm-sifive.yaml

@@ -25,12 +25,15 @@ description:
 properties:
   compatible:
     items:
-      - const: sifive,fu540-c000-pwm
+      - enum:
+          - sifive,fu540-c000-pwm
+          - sifive,fu740-c000-pwm
       - const: sifive,pwm0
     description:
       Should be "sifive,<chip>-pwm" and "sifive,pwm<version>". Supported
-      compatible strings are "sifive,fu540-c000-pwm" for the SiFive PWM v0
-      as integrated onto the SiFive FU540 chip, and "sifive,pwm0" for the
+      compatible strings are "sifive,fu540-c000-pwm" and
+      "sifive,fu740-c000-pwm" for the SiFive PWM v0 as integrated onto the
+      SiFive FU540 and FU740 chip respectively, and "sifive,pwm0" for the
       SiFive PWM v0 IP block with no chip integration tweaks.
       Please refer to sifive-blocks-ip-versioning.txt for details.