Fixed an uninitialized diagnostic id

- This diagnostic id was uninitialized but queried. We generally always
  explicitly set ids to -1 even if a later register call will set it.
  In this case, valgrind said it was being looked at before being set.

src/ALE/MOM_ALE.F90

@@ -95,7 +95,7 @@ module MOM_ALE
   integer, dimension(:), allocatable :: id_Htracer_remap_tendency     !< diagnostic id
   integer, dimension(:), allocatable :: id_Htracer_remap_tendency_2d  !< diagnostic id
   logical, dimension(:), allocatable :: do_tendency_diag              !< flag for doing diagnostics
-  integer                            :: id_dzRegrid
+  integer                            :: id_dzRegrid = -1              !< diagnostic id
 
 end type