batman-adv: drop dependency against CRC16

The crc16 functionality is not used anymore, therefore
we can safely remove the dependency in the Kbuild file.
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>

net/batman-adv/Kconfig

@@ -5,7 +5,6 @@
 config BATMAN_ADV
 	tristate "B.A.T.M.A.N. Advanced Meshing Protocol"
 	depends on NET
-	select CRC16
 	select LIBCRC32C
         default n
 	help