drm/msm: Ensure vm is created in VM_BIND ioctl

Since the vm is lazily created, to allow userspace to opt-in to a
VM_BIND context, we can't assume it is already created.

Fixes: 2e6a8a1 ("drm/msm: Add VM_BIND ioctl")
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/682939/
Message-ID: <20251022222039.9937-1-robin.clark@oss.qualcomm.com>

Author: Rob Clark

drivers/gpu/drm/msm/msm_gem_vma.c

@@ -1407,7 +1407,7 @@ msm_ioctl_vm_bind(struct drm_device *dev, void *data, struct drm_file *file)
 	 * Maybe we could allow just UNMAP ops?  OTOH userspace should just
 	 * immediately close the device file and all will be torn down.
 	 */
-	if (to_msm_vm(ctx->vm)->unusable)
+	if (to_msm_vm(msm_context_vm(dev, ctx))->unusable)
 		return UERR(EPIPE, dev, "context is unusable");
 
 	/*