dt-bindings: perf: riscv,pmu: drop unneeded quotes

Drop unneeded quotes over simple string values to fix a soon to be
enabled yamllint warning:

  [error] string value is redundantly quoted with any quotes (quoted-strings)

Signed-off-by: Rob Herring <[email protected]>
Reviewed-by: Krzysztof Kozlowski <[email protected]>
Acked-by: Conor Dooley <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

Documentation/devicetree/bindings/perf/riscv,pmu.yaml

@@ -90,7 +90,7 @@ properties:
             bitmap of all MHPMCOUNTERx that can monitor the range of events
 
 dependencies:
-  "riscv,event-to-mhpmevent": [ "riscv,event-to-mhpmcounters" ]
+  riscv,event-to-mhpmevent: [ "riscv,event-to-mhpmcounters" ]
 
 required:
   - compatible