Bluetooth: Fix ERTM L2CAP resend packet

I-Frame which is going to be resend already has FCS field added and set
(if it was required). Adding additional FCS field calculated from data +
old FCS in resend function is incorrect. This patch fix that.

Issue has been found during PTS testing.

Change-Id: Iba211a180665c5f2fa2fa462f5d5c48e2d980a21
Signed-off-by: Lukasz Rymanowski <lukasz.rymanowski@tieto.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Git-commit: 13cac15296afe7e42088ecfcd0f1d4b658248c46
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Kamal Negi <kamaln@codeaurora.org>