drm/msm: make sure last_fence is always updated

In the Linux kernel, the following vulnerability has been resolved: drm/msm: make sure last_fence is always updated Update last_fence in the vm-bind path instead of kernel managed path. last_fence is used to wait for work to finish in vm_bind contexts but not used for kernel managed contexts. This fixes a bug where last_fence is not waited on context close leading to faults as resources are freed while in use. Patchwork: https://patchwork.freedesktop.org/patch/680080/