net: 6lo: Fix source address uncompression

When src and dst addresses are compressed based on context
information, uncompression method should verify CID bit,
SAC and DAC bits and context ID's. But it has missed some
cases which resulted in invalid uncompressed IPv6 header.

e.g. CID is set, SAC is 0 and DAC is 1 and context id's provided.
Uncompression method assumed that src address is compressed based
on context information but it is not.

Signed-off-by: Ravi kumar Veeramally <ravikumar.veeramally@linux.intel.com>