iwlwifi: mvm: add soc latency support

Some devices require longer time to stabilize the power and XTAL.
This is especially true for devices integrated in the SoC.  Add
support for a new firmware API that allows the driver to set the
latency value accordingly.

Change-Id: I6829a46b89e4e701f80a0e4033f4dd41ee44ed12
Signed-off-by: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>