nvmem: make nvmem_add_cells() static

Now we have new api nvmem_add/del_cell_table() we do not want users to use
nvmem_add_cells() anymore. So mark it accordingly. I guess it was missed in
original cleanup patch.

This also fixes below warning:
core.c:355:5: warning: no previous prototype for 'nvmem_add_cells'
 [-Wmissing-prototypes]
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/core.c

@@ -352,7 +352,7 @@ static int nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
  *
  * Return: 0 or negative error code on failure.
  */
-int nvmem_add_cells(struct nvmem_device *nvmem,
+static int nvmem_add_cells(struct nvmem_device *nvmem,
 		    const struct nvmem_cell_info *info,
 		    int ncells)
 {
@@ -391,7 +391,6 @@ int nvmem_add_cells(struct nvmem_device *nvmem,
 
 	return rval;
 }
-EXPORT_SYMBOL_GPL(nvmem_add_cells);
 
 /*
  * nvmem_setup_compat() - Create an additional binary entry in