abis_nm: fix length indicator in Set Channel Attributes

This message may contain optional IEs (HSN, MAIO, ARFCN list),
so we cannot know the final length in advance. Let's set both
msg->{l2h,l3h} pointers and use msgb_l3len() to get the length.

Change-Id: I948ad4b847921324794a6eabd95d5583324da6e4
Related: OS#4545
1 file changed