[media] saa7134: avoid complex macro warnings

The debug macros are not properly defined, as they generate warnings
like:

ERROR: Macros with complex values should be enclosed in parentheses
+#define core_dbg(fmt, arg...)    if (core_debug) \
+	printk(KERN_DEBUG pr_fmt("core: " fmt), ## arg)

Use do { } while (0) for those macros.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>