caif: Fixed potential memory leak

Rearranged the allocation and packet creations to
avoid potential leaks in error path.

Signed-off-by: Kim Lilliestierna <kim.xx.lilliestierna@stericsson.com>
Signed-off-by: Sjur Brændeland <sjur.brandeland@stericssion.com>
Signed-off-by: David S. Miller <davem@davemloft.net>