powerpc/eeh: Export eeh_pe_state_mark()

This exports eeh_pe_state_mark(). It will be used to mark the surprise
hot removed PE as isolated to avoid unexpected EEH error reporting in
surprise remove path.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>