qcacmn: Remove csum_enabled flag and related changes

As part of code change we are removing csum_enabled flag check.
In that case, csum_enabled becomes redundant since we are not using it
in the code base, So remove redundant code as part of the cleanup.

Change-Id: Iac411b20f06436053b1969a1af9e3b3ee418c34c
CRs-Fixed: 3070858