ANDROID: Incremental fs: Fix dangling else

Fix a compiler warning:

    fs/incfs/data_mgmt.c: In function ‘incfs_get_filled_blocks’:
    fs/incfs/data_mgmt.c:768:6: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wdangling-else]
      768 |   if (is_data_block_present(&dfb))
          |      ^

Fixes: 9cbdd375f644 ("ANDROID: Incremental fs: Fix filled block count from get filled blocks")
Change-Id: I5a331442155443c6f67e33f1bbaf5deae84a644b
Signed-off-by: Eric Biggers <ebiggers@google.com>