printk: fix regression in SYSLOG_ACTION_CLEAR

Commit 7ff9554bb578ba02166071d2d487b7fc7d860d62 (printk: convert
byte-buffer to variable-length record buffer) introduced a regression
by accidentally removing a "break" statement from inside the big
switch in printk's do_syslog().  The symptom of this bug is that the
"dmesg -C" command doesn't only clear the kernel's log buffer; it also
disables console logging.

This patch (as1561) fixes the regression by adding the missing
"break".

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kernel/printk.c

@@ -1040,6 +1040,7 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
 	/* Clear ring buffer */
 	case SYSLOG_ACTION_CLEAR:
 		syslog_print_all(NULL, 0, true);
+		break;
 	/* Disable logging to console */
 	case SYSLOG_ACTION_CONSOLE_OFF:
 		if (saved_console_loglevel == -1)