p4080ds: remove rev1-specific code for the SERDES8 erratum

Remove the SERDES8 erratum work-around code that only applied to P4080
rev1, which is not supported by this version of U-Boot.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>