firmware: zynqmp: Do not report error if node is already configured

Power domain driver sends PM fragment to PMUFW. It is sent for every node
which is listed in DT. But some nodes could be already enabled but driver
is not capable to find it out. That's why it blinly sents request for every
listed IP. When PMUFW response by XST_PM_ALREADY_CONFIGURED error code
there is no need to show any error message because node is already enabled.
That's why cover this case with message when DEBUG is enabled.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/8c15ef0b68cf191f693d3d010f70ac24cfd8171f.1642163135.git.michal.simek@xilinx.com