wifi: ath6kl: minor fix for allocation size

wifi: ath6kl: minor fix for allocation size

[ Upstream commit 778f83f889e7fca37780d9640fcbd0229ae38eaa ]

Although the "param" pointer occupies more or equal space compared
to "*param", the allocation size should use the size of variable
itself.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: e0374f4be59b86a7 ("Add ath6kl cleaned up driver")
Signed-off-by: Alexey V. Vissarionov <gremlin@altlinux.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230117110414.GC12547@altlinux.org
Signed-off-by: Sasha Levin <sashal@kernel.org>