arm64: dts: arm: drop unused interrupt-names in MHU

The arm,mhu bindings and driver do not define interrupt-names, so drop
the property to fix warnings:

  arch/arm64/boot/dts/arm/juno-r2.dt.yaml: mhu@2b1f0000: 'interrupt-names' does not match any of the regexes: 'pinctrl-[0-9]+'

Link: https://lore.kernel.org/r/20210820081733.83976-3-krzysztof.kozlowski@canonical.comAcked-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

arch/arm64/boot/dts/arm/juno-base.dtsi

@@ -27,8 +27,6 @@ mailbox: mhu@2b1f0000 {
 		reg = <0x0 0x2b1f0000 0x0 0x1000>;
 		interrupts = <GIC_SPI 36 IRQ_TYPE_LEVEL_HIGH>,
 			     <GIC_SPI 35 IRQ_TYPE_LEVEL_HIGH>;
-		interrupt-names = "mhu_lpri_rx",
-				  "mhu_hpri_rx";
 		#mbox-cells = <1>;
 		clocks = <&soc_refclk100mhz>;
 		clock-names = "apb_pclk";