dt-bindings: mmc: starfive: Remove properties from required

Due to the change of tuning implementation, it's no longer necessary to
use the "starfive,sysreg" property in dts, so remove it from required.
Signed-off-by: William Qiu <william.qiu@starfivetech.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Link: https://lore.kernel.org/r/20230922062834.39212-2-william.qiu@starfivetech.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/starfive,jh7110-mmc.yaml

@@ -55,7 +55,6 @@ required:
   - clocks
   - clock-names
   - interrupts
-  - starfive,sysreg
 
 unevaluatedProperties: false
 
@@ -73,5 +72,4 @@ examples:
         fifo-depth = <32>;
         fifo-watermark-aligned;
         data-addr = <0>;
-        starfive,sysreg = <&sys_syscon 0x14 0x1a 0x7c000000>;
     };