iwlagn: modify digital SVR for 1000

On 1000, there are two Switching Voltage Regulators (SVR). The first one
apply digital voltage level (1.32V) for PCIe block and core. We need to
use this regulator to solve a stability issue related to noisy DC2DC
line in the silicon.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>