6lowpan: use IS_SRC and IS_DEST defines

These defines is to identify for which address the uncompress
address function do a uncompress.

There are two options for a source address or destination address.
6lowpan: remove jump over CID bit

Context based compression is currently not supported and we don't
do anything with this CID bit.

This patch removes to jump over the inline byte.
6lowpan: remove not used arrays
6lowpan: add brackets in for loop

Keep in linux codeing style.