board/beagleboneai/genimage.cfg: beautify file

Beatify this genimage .cfg file to have consistency with all genimage .cfg
files in Buildroot.

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

board/beagleboneai/genimage.cfg

@@ -8,6 +8,7 @@ image boot.vfat {
 			"uEnv.txt"
 		}
 	}
+
 	size = 16M
 }