[FS#210] ltq-RFC4638 PPPoE MTU support

[LEDE Bugs]

The following task is now closed:

FS#210 - ltq-RFC4638 PPPoE MTU support
User who did this - Mathias Kresin (mkresin)

Reason for closing: Implemented
Additional comments about closing: https://git.lede-project.org/8a2a20e71e2909f84dab47e51dfda9e292a6c1ae

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=210