ath11k: fix memory leak on reg_info

Currently a return path is leaking the previously allocate reg_info. Fix
this by exiting via the return path mem_free.  Since the return value ret
is defaulted to 0, there is no need to re-assign ret to the 0 before
the goto.

Addresses-Coverity: ("Resource leak")
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>