msm: Kconfig: make MSM_QDSP6_APRV2 dependant on MSM_AUDIO_QDSP6V2

Defining MSM_QDSP6_APRV2 without MSM_AUDIO_QDSP6V2 causes linking errors
for other kernel modules as the APR module isn't actually being
compiled.

Change-Id: I2ac5de51c7b3cec6bf1d318b6a3ce7fe52ea4d90
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>