misc/ompl: Fix duplicate target "post-patch-PLANNERARENA-off"

The .for loop iterated over all options except DEMOS, which included
PLANNERARENA. This generated a post-patch-PLANNERARENA-off target that
conflicted with the explicit one defined after the loop.

Fix by:

• Exempting PLANNERARENA from the .for loop
• Adding the missing PLANNERARENA option variables (DESC, BUILD_DEPENDS, RUN_DEPENDS) that were previously removed

PR: 295634
Approved by: yuri (maintainer, timeout 2 weeks)