iwlwifi: mvm: split constants into separate file

To make maintaining some constant default values in the
driver easier, declare them in a separate file.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc drivers/net/wireless/iwlwifi/mvm/constants.h
Simple merge

diff --cc drivers/net/wireless/iwlwifi/mvm/mvm.h
Simple merge

diff --cc drivers/net/wireless/iwlwifi/mvm/power.c
Simple merge