Arm: msm: Kconfig: disable QDPSV6 on mdm9640

QDSPV6 fails to compile with msm-3.18 for mdm9640.
Disable it until the compilation failures are
fixed.

Change-Id: I302c3be3b99aca43c33457219a7f5746408752fe
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>