ASoC: msm-lsm-client: Validate size sent from userspace

The payload size for keyword detection event status is received from
userspace through IOCTL. This payload size is used to allocate memory in
the driver. Validate the payload size before memory allocation to make
sure the payload size is within the maximum allowed size.

CRs-fixed: 842347
Change-Id: I268dc4b9c7b0219aadac221b2dd0003ea3b4dbad
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>