Revert "lpdc: fix for jumbo frames"

This reverts commit 9a26b13e.
3 jobs from v7.0-back-to-v6.0 in 103 minutes and 20 seconds (queued for 1 second)
Status Job ID Name Coverage
  Sim
manual #15391
modelsim_10.2a allowed to fail manual
job_scb_top_sim
 
  Syn
passed #15393
xilinx_ISE_14.7 allowed to fail manual
job_scb_top_18p_syn

01:43:04

canceled #15392
xilinx_ISE_14.7
job_scb_top_8p_syn

00:16