rtw88: fix sparse warnings for power tracking

sparse warnings:
    drivers/net/wireless/realtek/rtw88/rtw8822b.c:1440:6: sparse: sparse:
    symbol 'rtw8822b_pwr_track' was not declared. Should it be static?
    drivers/net/wireless/realtek/rtw88/rtw8822c.c:1008:6: sparse: sparse:
    symbol 'rtw8822c_pwrtrack_init' was not declared. Should it be static?

Fixes: c97ee3e0 ("rtw88: add power tracking support")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>