ptp: fix missing break in switch

BugLink: https://bugs.launchpad.net/bugs/1791080

[ Upstream commit 9ba8376c ]

It seems that a *break* is missing in order to avoid falling through
to the default case. Otherwise, checking *chan* makes no sense.

Fixes: 72df7a72 ("ptp: Allow reassigning calibration pin function")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/ptp/ptp_chardev.c

@@ -89,6 +89,7 @@ int ptp_set_pinfunc(struct ptp_clock *ptp, unsigned int pin,
 	case PTP_PF_PHYSYNC:
 		if (chan != 0)
 			return -EINVAL;
+		break;
 	default:
 		return -EINVAL;
 	}