qcacmn: Clean CONFIG_MCL for send_flush_completion_to_user

The aim is to remove CONFIG_MCL or CONFIG_WIN from
cmn component.

This change takes care send_flush_completion_to_user.
Cleaning up cmn code by replacing the CONFIG_MCL
with macro FEATURE_WLAN_DIAG_SUPPORT.

CRs-Fixed: 2397824
Change-Id: I57a82fec17210b49f778a950034ca442d11eb511
1 file changed