rtlwifi: btcoex: Remove set but not used variable 'len' and 'asso_type_v2'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/realtek/rtlwifi/btcoexist/rtl_btc.c: In function rtl_btc_btmpinfo_notify:
drivers/net/wireless/realtek/rtlwifi/btcoexist/rtl_btc.c:319:17: warning: variable len set but not used [-Wunused-but-set-variable]
drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtcoutsrc.c: In function exhalbtc_connect_notify:
drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtcoutsrc.c:1581:16: warning: variable asso_type_v2 set but not used [-Wunused-but-set-variable]

'len' is never used since commit 6aad6075 ("rtlwifi:
Add BT_MP_INFO to c2h handler.") so can be removed.

'asso_type_v2' is not used since introduction in
commit 0843e98a

 ("rtlwifi: btcoex: add assoc
type v2 to connection notify")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>