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