ath11k: fix uninitialized variable radioup

The variable radioup is not uninitalized so it may contain a garbage
value and hence the detection of a radio that is not up is buggy.
Fix this by initializing it to zero.

Addresses-Coverity: ("Uninitalized scalar variable")
Fixes: d5c65159 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>