www/linux-*-flashplugin11: set -c6 port as master port

• Make www/linux-c6-flashplugin11 master port
• Make www/linux-f10-flashplugin11 slave port
• Reduce future maintenance turnaround.

Differential Revision: https://reviews.freebsd.org/D2128
Reviewed by: eadler
Approved by: koobs (mentor)