arm64: dts: juno: replace underscores with hyphen in device node names

Since underscores('_') are not allowed in the device tree nodes names,
replace all of them with hyphen('-') in device node names. Note that
underscores are however allowed in labels.

Reported-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>