wifi: rtw89: cleanup rtw89_iqk_info and related code

Drop useless '_iqk_track()' and 'rtw8852a_iqk_track()' (they
just change 'thermal_rek_en' field which is set but unused
and so removed as well) functions, set but unused 'kcount'
field of 'struct rtw89_iqk_info', and convert 'thermal' to
local variables where appropriate (it doesn't need to have
longer storage duration because it is actually used for the
debugging purposes only).

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230614081555.91395-2-dmantipov@yandex.ru