[cmake] fix capitalization of some SuiteSparse_ variables

There were still some variables with the old capitalization SUITESPARSE_ that prevented my own code from finding umfpack.h.

After this small fix, the code from merge request !8 (merged) works for me as expected.

cmake/modules/AddSuiteSparseFlags.cmake

@@ -11,13 +11,13 @@
#
function(add_dune_suitesparse_flags _targets)
-  if(SUITESPARSE_FOUND)
+  if(SuiteSparse_FOUND)
foreach(_target ${_targets})
-      target_link_libraries(${_target} ${SUITESPARSE_DUNE_LIBRARIES})
+      target_link_libraries(${_target} ${SuiteSparse_DUNE_LIBRARIES})
get_target_property(_props ${_target} COMPILE_FLAGS)
string(REPLACE "_props-NOTFOUND" "" _props "${_props}")
set_target_properties(${_target} PROPERTIES COMPILE_FLAGS
-        "${_props} ${SUITESPARSE_DUNE_COMPILE_FLAGS} -DENABLE_SUITESPARSE=1")
+        "${_props} ${SuiteSparse_DUNE_COMPILE_FLAGS} -DENABLE_SUITESPARSE=1")
endforeach(_target ${_targets})
-  endif(SUITESPARSE_FOUND)
+  endif(SuiteSparse_FOUND)
endfunction(add_dune_suitesparse_flags)