[IA64-SGI] Remove SN SAL error handling feature bit that is no longer needed

Due to improvements in linux & SAL MCA handling, the
SAL_ERR_FEAT_MCA_SLV_TO_OS_INIT_SLV error handling features bit
is no longer needed.

Signed-off-by: Russ Anderson <(rja@sgi.com)>
Signed-off-by: Tony Luck <tony.luck@intel.com>