rockchip: px30: Use new bl31_params_parse functions

This change is needed for the platform to compile following the changes
made in commits cbdc72b559ab and 3e02c7436cf4.

Change-Id: I3468dd27f3b4f3095fb82f445d51cd8714311eb7
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
1 file changed