There are two returns in the switch in sc_ioctl (the SCIOCSTART case) that
may leak `rcvmsg'. This patch fixes that by adding a kfree() call at the
beginning of that case.
Bug found by the coverity checker as #1098
Eric Sesterhenn send me a patch to fix the leak(s) by adding 2 kfree()
calls before the returns, I changed that into just a single call at the
beginning.