arm64: zynqmp: Fix return code from do_zynqmp_pmufw()

zynqmp_pmufw_node() can also return values like -ENODEV which means that
NODE has been already configured that's why don't propagate this error
code.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/e52d24d8d3efb276778d387dc716e4e065e0626f.1685618701.git.michal.simek@amd.com