dt-bindings: phy: Fix errors in intel,lgm-emmc-phy example

DT labels can't have '-' in them causing a compile failure in the example.
Fixing that leads to more warnings:

Documentation/devicetree/bindings/phy/intel,lgm-emmc-phy.example.dts:23.13-33: Warning (reg_format): /example-0/chiptop@e0200000/emmc-phy@a8:reg: property has invalid length (8 bytes) (#address-cells == 2, #size-cells == 1)
Documentation/devicetree/bindings/phy/intel,lgm-emmc-phy.example.dt.yaml: Warning (pci_device_bus_num): Failed prerequisite 'reg_format'
Documentation/devicetree/bindings/phy/intel,lgm-emmc-phy.example.dt.yaml: Warning (i2c_bus_reg): Failed prerequisite 'reg_format'
Documentation/devicetree/bindings/phy/intel,lgm-emmc-phy.example.dt.yaml: Warning (spi_bus_reg): Failed prerequisite 'reg_format'
Documentation/devicetree/bindings/phy/intel,lgm-emmc-phy.example.dts:21.33-26.13: Warning (avoid_default_addr_size): /example-0/chiptop@e0200000/emmc-phy@a8: Relying on default #address-cells value
Documentation/devicetree/bindings/phy/intel,lgm-emmc-phy.example.dts:21.33-26.13: Warning (avoid_default_addr_size): /example-0/chiptop@e0200000/emmc-phy@a8: Relying on default #size-cells value

Fixes: 5bc99910 ("dt-bindings: phy: intel-emmc-phy: Add YAML schema for LGM eMMC PHY")
Cc: Ramuthevar Vadivel Murugan <vadivel.muruganx.ramuthevar@linux.intel.com>
Cc: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/phy/intel,lgm-emmc-phy.yaml

@@ -45,8 +45,10 @@ examples:
     sysconf: chiptop@e0200000 {
       compatible = "intel,lgm-syscon", "syscon";
       reg = <0xe0200000 0x100>;
+      #address-cells = <1>;
+      #size-cells = <1>;
 
-      emmc-phy: emmc-phy@a8 {
+      emmc_phy: emmc-phy@a8 {
         compatible = "intel,lgm-emmc-phy";
         reg = <0x00a8 0x10>;
         clocks = <&emmc>;