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

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 cbb1cb712168 ("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 <jrdr.linux@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>