iwlagn: more comments for bt channel inhibition

Add comments for better description

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --cc drivers/net/wireless/iwlwifi/iwl-agn-lib.c
Simple merge

diff --cc drivers/net/wireless/iwlwifi/iwl-agn.c
Simple merge

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