iwlwifi: pcie: make non-static hcmd and rx code

Allow other device generations to use the utilities that
are used to send and reclaim host commands and to allocate
rx, by making it non-static.

Signed-off-by: Golan Ben Ami <golan.ben.ami@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>