wifi: ath12k: hal_rx: Use memset_startat() for clearing queue descriptors

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Use memset_startat() so memset() doesn't get confused about writing
beyond the destination member that is intended to be the starting point
of zeroing through the end of the struct and fixes the below clang
warning.

Warning:
include/linux/fortify-string.h:314:4: warning: call to '__write_overflow_field' declared with 'warning' attribute:
detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0-03171-QCAHKSWPL_SILICONZ-1
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thiraviyam Mariyappan <quic_tmariyap@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20221221105529.19345-3-quic_tmariyap@quicinc.com