drivers-core: make structured logging play nice with dynamic-debug

commit c4e00daa changed __dev_printk
in a way that broke dynamic-debug's ability to control the dynamic
prefix of dev_dbg(dev,..), but not dev_dbg(NULL,..) or pr_debug(..),
which is why it wasnt noticed sooner.

When dev==NULL, __dev_printk() just calls printk(), which just works.
But otherwise, it assumed that level was always a string like "<L>"
and just plucked out the 'L', ignoring the rest.  However,
dynamic_emit_prefix() adds "[tid] module:func:line:" to the string,
those additions all got lost.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Acked-by: Jason Baron <jbaron@redhat.com>
Cc: stable <stable@vger.kernel.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -1865,6 +1865,7 @@ int __dev_printk(const char *level, const struct device *dev,
 		 struct va_format *vaf)
 {
 	char dict[128];
+	const char *level_extra = "";
 	size_t dictlen = 0;
 	const char *subsys;
 
@@ -1911,10 +1912,14 @@ int __dev_printk(const char *level, const struct device *dev,
 				    "DEVICE=+%s:%s", subsys, dev_name(dev));
 	}
 skip:
+	if (level[3])
+		level_extra = &level[3]; /* skip past "<L>" */
+
 	return printk_emit(0, level[1] - '0',
 			   dictlen ? dict : NULL, dictlen,
-			   "%s %s: %pV",
-			   dev_driver_string(dev), dev_name(dev), vaf);
+			   "%s %s: %s%pV",
+			   dev_driver_string(dev), dev_name(dev),
+			   level_extra, vaf);
 }
 EXPORT_SYMBOL(__dev_printk);