iwlwifi: mvm: make phy_db size dynamic

Driver is agnostic to the number of the phy_db entries and
only serves the firmware as a pipe to move the data from init
image to RT image.
As the size of the arrays may change (as it does in 9000 device)
allocate it dynamically. Firmware sends the largest index first
so we can use this to know how much we should allocate.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>