msm: pil-q6v5: Use container_of() to get q6v5_data

With the PIL descriptor embedded in the q6v5_data struct we can
use container_of() to find the data we want instead of indirectly
accessing the driver data via the desc->dev->platform_data field.
This is essential so we can combine the two modem pil drivers on
8974 (pil-mba and pil-q6v5-mss).

Change-Id: Ie2e0b471215cdb83ceebc808626775d25e8417e8
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>