iwlwifi: move iwl_get_single_channel_number and mark it static

iwl_get_single_channel_number is used only in
iwl-scan.c, move it there and mark it static.

Signed-off-by: Meenakshi Venkataraman <meenakshi.venkataraman@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
3 files changed