usnic: minor re-order of Makefile.am sources

Put the hwloc.c file alphabetically in the list.

(cherry picked from commit open-mpi/ompi@f782a76)

Author: jsquyres

opal/mca/btl/usnic/Makefile.am

@@ -49,6 +49,7 @@ sources = \
     btl_usnic_frag.h \
     btl_usnic_graph.h \
     btl_usnic_graph.c \
+    btl_usnic_hwloc.c \
     btl_usnic_hwloc.h \
     btl_usnic_map.c \
     btl_usnic_mca.c \
@@ -64,8 +65,7 @@ sources = \
     btl_usnic_util.h \
     btl_usnic_test.c \
     btl_usnic_test.h \
-    $(test_sources) \
-    btl_usnic_hwloc.c
+    $(test_sources)
 
 # Make the output library in this directory, and name it either
 # mca_<type>_<name>.la (for DSO builds) or libmca_<type>_<name>.la