tpm/tpm_ibmvtpm: fix unreachable code warning (smatch warning)

smatch complains:
drivers/char/tpm/tpm_ibmvtpm.c:510
ibmvtpm_crq_process() info: ignoring unreachable code.

-> The return is not necessary here, remove it
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>

drivers/char/tpm/tpm_ibmvtpm.c

@@ -507,7 +507,6 @@ static void ibmvtpm_crq_process(struct ibmvtpm_crq *crq,
 			dev_err(ibmvtpm->dev, "Unknown crq message type: %d\n", crq->msg);
 			return;
 		}
-		return;
 	case IBMVTPM_VALID_CMD:
 		switch (crq->msg) {
 		case VTPM_GET_RTCE_BUFFER_SIZE_RES: