defconfig: Remove CONFIG_CNSS_QCA6390

Remove QCA driver dependency from kernel configuration. Supported
chipset will be auto detected at run time.

Change-Id: I945a2eba8b9557500e2537f99a154cdc50a1c4fe
CRs-Fixed: 2661909
Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>