6lowpan: iphc: change define values

This patch has the main goal to delete shift operations. Instead we
doing masks and equals afterwards. E.g. for the SAM evaluation we
masking only the SAM value which fits in iphc1 byte, then comparing with
all possible SAM values over a switch case statement. We will not
shifting the SAM value to somewhat readable anymore.
Additional this patch slighty change the naming style like RFC 6282,
e.g. TTL to HLIM and we will drop an errno now if CID flag is set,
because we don't support it.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>