dm thin metadata: remove unused dm_pool_get_data_block_size()

The thin-pool target doesn't display the data block size as part of
its table status, unlike the dm-cache target, so there is no need for
dm_pool_get_data_block_size().

This was found using cppcheck.
Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-thin-metadata.c

@@ -1635,15 +1635,6 @@ int dm_pool_get_metadata_dev_size(struct dm_pool_metadata *pmd,
 	return r;
 }
 
-int dm_pool_get_data_block_size(struct dm_pool_metadata *pmd, sector_t *result)
-{
-	down_read(&pmd->root_lock);
-	*result = pmd->data_block_size;
-	up_read(&pmd->root_lock);
-
-	return 0;
-}
-
 int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result)
 {
 	int r = -EINVAL;

drivers/md/dm-thin-metadata.h

@@ -182,8 +182,6 @@ int dm_pool_get_free_metadata_block_count(struct dm_pool_metadata *pmd,
 int dm_pool_get_metadata_dev_size(struct dm_pool_metadata *pmd,
 				  dm_block_t *result);
 
-int dm_pool_get_data_block_size(struct dm_pool_metadata *pmd, sector_t *result);
-
 int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result);
 
 int dm_pool_block_is_used(struct dm_pool_metadata *pmd, dm_block_t b, bool *result);