arm64: zynqmp: Replace '-' by '_' in fixed clock nodes

Using '_' in node name is not recommended that's why convert them to use
'-' instead.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/3979167636f0a5970a9ab642a4e0ea6a46b3f8d7.1704705872.git.michal.simek@amd.com