wifi: iwlwifi: Separate loading and setting of pnvm image into two functions

Take the part that is copying the pnvm image into DRAM, out of the
the method that sets the prph_scratch. Makes the code cleaner since
those 2 operations don't always happen together (loading should happen
only once while setting can happen more than once).
In addition, each operation will get more complex in the future when
it will support also larger pnvm images.

Signed-off-by: Alon Giladi <alon.giladi@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230606103519.4c0728239fd6.Ibc30a9fbdb6123dadbe2dbb89318dbd5ec01080a@changeid


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