drm/msm: Fix NULL pointer dereference in crashstate_get_vm_logs()

drm/msm: Fix NULL pointer dereference in crashstate_get_vm_logs()

crashstate_get_vm_logs() did not check the return value of
kmalloc_array(). In low-memory situations, kmalloc_array() may return
NULL, leading to a NULL pointer dereference when the function later
accesses state->vm_logs.

Fix this by checking the return value of kmalloc_array() and setting
state->nr_vm_logs to 0 if allocation fails.

Fixes: 9edc52967cc7 ("drm/msm: Add VM logging for VM_BIND updates")
Signed-off-by: Huiwen He <hehuiwen@kylinos.cn>
Patchwork: https://patchwork.freedesktop.org/patch/687555/
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>