drivers/hwtracing/intel_th/msu.c: change return type to vm_fault_t

Use new return type vm_fault_t for fault handler. For now, this is just
documenting that the function returns a VM_FAULT value rather than an
errno. Once all instances are converted, vm_fault_t will become a
distinct type.

See 1c8f422059ae ("mm: change return type to vm_fault_t") for reference.

Link: http://lkml.kernel.org/r/20180702155801.GA4010@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/hwtracing/intel_th/msu.c

···
 	mutex_unlock(&msc->buf_mutex);
 }
 
-static int msc_mmap_fault(struct vm_fault *vmf)
+static vm_fault_t msc_mmap_fault(struct vm_fault *vmf)
 {
 	struct msc_iter *iter = vmf->vma->vm_file->private_data;
 	struct msc *msc = iter->msc;