staging: rtl8821ae: add static for local symbols in halbtcoutsrc.c

This commit fixes the sparse warning:

    "warning: symbol 'X' was not declared. Should it be static?"

Where the X is one of the following:

    bt_profile_string
    bt_spec_string
    bt_link_role_string
    h2c_state_string
    io_state_string
    btc_dbg_buf
    halbtc_is_bt_coexist_available
    halbtc_is_wifi_busy
    halbtc_dbg_init
    halbtc_is_hw_mailbox_exist
    halbtc_is_bt40
    halbtc_legacy
    halbtc_get_wifi_bw
    halbtc_get_wifi_central_chnl
    halbtc_leave_lps
    halbtc_enter_lps
    halbtc_normal_lps
    halbtc_leave_low_power
    halbtc_nomal_low_power
    halbtc_disable_low_power
    halbtc_aggregation_check
    halbtc_get_bt_patch_version
    halbtc_get_wifi_rssi
    halbtc_get
    halbtc_set
    halbtc_display_coex_statistics
    halbtc_display_bt_link_info
    halbtc_display_bt_fw_info
    halbtc_display_fw_pwr_mode_cmd
    halbtc_read_1byte
    halbtc_read_2byte
    halbtc_read_4byte
    halbtc_write_1byte
    halbtc_bitmask_write_1byte
    halbtc_write_2byte
    halbtc_write_4byte
    halbtc_set_macreg
    halbtc_get_macreg
    halbtc_set_bbreg
    halbtc_get_bbreg
    halbtc_set_rfreg
    halbtc_get_rfreg
    halbtc_fill_h2c_cmd
    halbtc_display_dbg_msg
    halbtc_under_ips
Signed-off-by: Konrad Zapalowicz <bergo.torino@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>