driver-core: use 'dev' argument in dev_dbg_ratelimited stub

dev_dbg_ratelimited() is a macro that ignores its first argument when DEBUG is
not set, which can lead to unused variable warnings:

ethernet/mellanox/mlxsw/pci.c: In function 'mlxsw_pci_cqe_sdq_handle':
ethernet/mellanox/mlxsw/pci.c:646:18: warning: unused variable 'pdev' [-Wunused-variable]
ethernet/mellanox/mlxsw/pci.c: In function 'mlxsw_pci_cqe_rdq_handle':
ethernet/mellanox/mlxsw/pci.c:671:18: warning: unused variable 'pdev' [-Wunused-variable]

The macro already ensures that all its other arguments are silently
ignored by the compiler without triggering a warning, through the
use of the no_printk() macro, but the dev argument is not passed into
that.

This changes the definition to use the same trick as no_printk() with
an if(0) that leads the compiler to not evaluate the side-effects but
still see that 'dev' might not be unused.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Fixes: 6f586e66 ("driver-core: Shut up dev_dbg_reatelimited() without DEBUG")
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/device.h

@@ -1294,7 +1294,10 @@ do {									\
 } while (0)
 #else
 #define dev_dbg_ratelimited(dev, fmt, ...)				\
-	no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+do {									\
+	if (0)								\
+		dev_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__);	\
+} while (0)
 #endif
 
 #ifdef VERBOSE_DEBUG