wifi: ath11k: fix NULL dereference in ath11k_qmi_m3_load()

If ab->fw.m3_data points to data, then fw pointer remains null.
Further, if m3_mem is not allocated, then fw is dereferenced to be
passed to ath11k_err function.

Replace fw->size by m3_len.

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

Fixes: 7db88b96 ("wifi: ath11k: add firmware-2.bin support")
Cc: stable@vger.kernel.org
Signed-off-by: Matvey Kovalev <matvey.kovalev@ispras.ru>
Reviewed-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20250917192020.1340-1-matvey.kovalev@ispras.ru


Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>