bugfix: remove loop-name col

Error message:
```
eclm/enkf_clm_mod_5.F90(264): error #6401: The attributes of this name
conflict with those made accessible by a USE statement.   [COL]
```

Author: jjokella

bldsva/intf_DA/pdaf/model/clm5_0/enkf_clm_mod_5.F90

@@ -256,14 +256,14 @@ subroutine define_clm_statevec(mype)
       do cc=1,clm_statevecsize
 
         lay: do i=1,nlevsoi
-          col: do c=clm_begc,clm_endc
+          do c=clm_begc,clm_endc
             if (state_clm2pdaf_p(c,i) == cc) then
               ! Set column index and then exit loop
               state_pdaf2clm_c_p(cc) = c
               state_pdaf2clm_j_p(cc) = i
               exit lay
             end if
-          end do col
+          end do
         end do lay
 
 #ifdef PDAF_DEBUG

bldsva/intf_DA/pdaf/model/eclm/enkf_clm_mod_5.F90

@@ -256,14 +256,14 @@ subroutine define_clm_statevec(mype)
       do cc=1,clm_statevecsize
 
         lay: do i=1,nlevsoi
-          col: do c=clm_begc,clm_endc
+          do c=clm_begc,clm_endc
             if (state_clm2pdaf_p(c,i) == cc) then
               ! Set column index and then exit loop
               state_pdaf2clm_c_p(cc) = c
               state_pdaf2clm_j_p(cc) = i
               exit lay
             end if
-          end do col
+          end do
         end do lay
 
 #ifdef PDAF_DEBUG