rtw89: Remove redundant check of ret after call to rtw89_mac_enable_bb_rf

The function rtw89_mac_enable_bb_rf is a void return type, so there is
no return error code to ret, so the following check for an error in ret
is redundant dead code and can be removed.

Addresses-Coverity: ("Logically dead code")
Fixes: e3ec7017 ("rtw89: add Realtek 802.11ax driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211015152113.33179-1-colin.king@canonical.com