ppc: define a default LPCR value

ppc: define a default LPCR value

This allows us to set the appropriate LPCR bits which will be used
when fixing the exception model for the HV mode.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
[clg: previous commit 26a7f1291bb5 did not include the LPCR setting as
      it was not needed at the time, adapted commit log ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>