i2c: cp2615: check for allocation failure in cp2615_i2c_recv()

We need to add a check for if the kzalloc() fails.

Fixes: 4a769542

 ("i2c: cp2615: add i2c driver for Silicon Labs' CP2615 Digital Audio Bridge")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Bence Csókás <bence98@sch.bme.hu>
Signed-off-by: Wolfram Sang <wsa@kernel.org>