ipm: mcux: Initialize variable before using it

Since the driver is passing the whole buffer, let's zero it to avoid
pass garbage in case of size != buffer's size.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
(cherry picked from commit 4ff32d9290da561365f063aa0c4394bc6d531e0d)
1 file changed