wifi: ath11k: mac: fix reading 16 bytes from a region of size 0 warning

Linaro reported stringop-overread warnings in ath11k (this is one of many):

drivers/net/wireless/ath/ath11k/mac.c:2238:29: error: 'ath11k_peer_assoc_h_he_limit' reading 16 bytes from a region of size 0 [-Werror=stringop-overread]

My further investigation showed that these warnings happen on GCC 11.3 but not
with GCC 12.2, and with only the kernel config Linaro provided:

https://builds.tuxbuild.com/2F4W7nZHNx3T88RB0gaCZ9hBX6c/config

I saw the same warnings both with arm64 and x86_64 builds and KASAN seems to be
the reason triggering these warnings with GCC 11.  Nobody else has reported
this so this seems to be quite rare corner case. I don't know what specific
commit started emitting this warning so I can't provide a Fixes tag. The
function hasn't been touched for a year.

I decided to workaround this by converting the pointer to a new array in stack,
and then copying the data to the new array. It's only 16 bytes anyway and this
is executed during association, so not in a hotpath.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.9

Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Link: https://lore.kernel.org/all/CA+G9fYsZ_qypa=jHY_dJ=tqX4515+qrV9n2SWXVDHve826nF7Q@mail.gmail.com/
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221010160638.20152-1-kvalo@kernel.org