firmware: zynqmp: Report error when xilinx_pm_request called from EL3

Function should report error when called in EL3 context. Also report it as
error instead 0 (success).

Reported-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
1 file changed