ath11k: Fix an error handling path in ath11k_core_fetch_board_data_api_n()

All error paths but this one 'goto err' in order to release some
resources.
Fix this.

Fixes: d5c65159 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/e959eb544f3cb04258507d8e25a6f12eab126bde.1621676864.git.christophe.jaillet@wanadoo.fr