powerpc/powernv: Move GET_FIELD/SET_FIELD to vas.h

powerpc/powernv: Move GET_FIELD/SET_FIELD to vas.h

BugLink: http://bugs.launchpad.net/bugs/1718293
Move the GET_FIELD and SET_FIELD macros to vas.h as VAS and other
users of VAS, including NX-842 can use those macros.

There is a lot of related code between the VAS/NX kernel drivers
and skiboot. For consistency, switch the order of parameters in
SET_FIELD to match the order in skiboot.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
(cherry picked from commit b6622a339e8670a1025d4dd84be473c76dabed33)
Signed-off-by: Gustavo Walbon <gwalbon@linux.vnet.ibm.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>