rp-pppoe: Port from oe.dev

The difference between this and oe.dev are:
- Reset PR
- Add bitfields site variable to the endian site file
  This was wrong in oe.dev for BE (mips).
- Add LIC_FILES_CHKSUM

Signed-off-by: Tom Rini <tom_rini@mentor.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>