fix(layerscape): update WA for Errata A-050426

Update WA for Errata A-050426 as Commands for
PEX (PEX1..PEX6) , lnx1_e1000#0, lnx1_xfi and
lnx2_xfi has been moved to PBI phase.

This patch requires RCW to include PBI commands
to write commands in BIST mode for PEX, lnx1_e1000,
lnx1_xfi and lnx2_xfi IP blocks.

Signed-off-by: Wasim Khan <wasim.khan@nxp.com>
Change-Id: I27c2b055c82c0b58df83449f9082bfbfdeb65115