swtpm: Remove SWTPM_IO_GetSocketFD and SWTPM_IO_SetSocketFD

SWTPM_IO_SetSocketFD was always passing mlp.fd before entering the main
loop and SWTPM_IO_GetSocketFD was then effectively getting mlp.fd while
in the main loop. In the main loop set sockfd from mlp->fd directly now.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>