powerpc/85xx: Add support for P2041[e] XAUI in SERDES

We add XAUI_FM1 into the SERDES tables for P2041[e] devices.  However
for the P2040[e] devices that dont support XAUI we handle this at
runtime via SVR checks.  If we are on a P2040[e] device the SERDES
functions will behave as follows:

is_serdes_prtcl_valid() will always report invalid if prtcl passed in is
XAUI_FM1.

serdes_get_prtcl() will report NONE if the prtcl in the table is set to
XAUI_FM1.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>