fbdev: via: fix -Wextra build warning and format warning

When 'VIAFB_DEBUG' and 'VIAFB_WARN' are not defined, modify the
DEBUG_MSG() &WARN_MSG() macros to use the no_printk() macro instead of
using <empty>.
This fixes a build warning when -Wextra is used and provides
printk format checking:

../drivers/video/fbdev/via/ioctl.c:88:47: warning: suggest braces around empty body in an ‘else’ statement [-Wempty-body]

Also use %lu to print an unsigned long instead of just %l, to fix
a printk format warning:

../drivers/video/fbdev/via/viafbdev.c: In function ‘viafb_dvp0_proc_write’:
../drivers/video/fbdev/via/viafbdev.c:1148:14: warning: unknown conversion type character ‘]’ in format [-Wformat=]
    DEBUG_MSG("DVP0:reg_val[%l]=:%x\n", i,
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Antonino Daplas <adaplas@gmail.com>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200315041002.24473-7-rdunlap@infradead.org

drivers/video/fbdev/via/debug.h

@@ -7,6 +7,8 @@
 #ifndef __DEBUG_H__
 #define __DEBUG_H__
 
+#include <linux/printk.h>
+
 #ifndef VIAFB_DEBUG
 #define VIAFB_DEBUG 0
 #endif
@@ -14,14 +16,14 @@
 #if VIAFB_DEBUG
 #define DEBUG_MSG(f, a...)   printk(f, ## a)
 #else
-#define DEBUG_MSG(f, a...)
+#define DEBUG_MSG(f, a...)   no_printk(f, ## a)
 #endif
 
 #define VIAFB_WARN 0
 #if VIAFB_WARN
 #define WARN_MSG(f, a...)   printk(f, ## a)
 #else
-#define WARN_MSG(f, a...)
+#define WARN_MSG(f, a...)   no_printk(f, ## a)
 #endif
 
 #endif /* __DEBUG_H__ */

drivers/video/fbdev/via/viafbdev.c

@@ -1144,7 +1144,7 @@ static ssize_t viafb_dvp0_proc_write(struct file *file,
 		if (value != NULL) {
 			if (kstrtou8(value, 0, &reg_val) < 0)
 				return -EINVAL;
-			DEBUG_MSG(KERN_INFO "DVP0:reg_val[%l]=:%x\n", i,
+			DEBUG_MSG(KERN_INFO "DVP0:reg_val[%lu]=:%x\n", i,
 				  reg_val);
 			switch (i) {
 			case 0: