intel_th: msu: Replace open-coded list_{first,last,next}_entry variants

There are a few places in the code where open-coded versions of list entry
accessors list_first_entry()/list_last_entry()/list_next_entry() are used.

Replace those with the standard macros.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>