net: move 6lowpan compression code to separate module

IEEE 802.15.4 and Bluetooth networking stacks share 6lowpan compression
code. Instead of introducing Makefile/Kconfig hacks, build this code as
a separate module referenced from both ieee802154 and bluetooth modules.

This fixes the following build error observed in some kernel
configurations:

net/built-in.o: In function `header_create': 6lowpan.c:(.text+0x166149): undefined reference to `lowpan_header_compress'
net/built-in.o: In function `bt_6lowpan_recv': (.text+0x166b3c): undefined reference to `lowpan_process_data'

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Dmitry Eremin-Solenikov <dmitry_eremin@mentor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/net/bluetooth/Kconfig b/net/bluetooth/Kconfig
index d3f3f7b1d32c..985b56070d26 100644
--- a/net/bluetooth/Kconfig
+++ b/net/bluetooth/Kconfig
@@ -12,6 +12,7 @@ menuconfig BT
         select CRYPTO_AES
         select CRYPTO_ECB
         select CRYPTO_SHA256
+        select 6LOWPAN_IPHC
         help
           Bluetooth is low-cost, low-power, short-range wireless technology.
           It was designed as a replacement for cables and other short-range