arm64: dts: Update cache properties for synaptics

The DeviceTree Specification v0.3 specifies that the cache node
'compatible' and 'cache-level' properties are 'required'. Cf.
s3.8 Multi-level and Shared Cache Nodes
The 'cache-unified' property should be present if one of the
properties for unified cache is present ('cache-size', ...).

Update the Device Trees accordingly.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Jisheng Zhang <jszhang@kernel.org>