spa: support: do not include C source file

Previously, `log-patterns.c` was included in two other source files
(`journal.c` and `logger.c`). It was also specified in the sources
list for the libspa-support library, which resulted in the unnecessary
independent compilation of the file, generating "defined but not used"
warnings.

Extract the function definitions into `log-patterns.h` and
use that in `journal.c` and `logger.c`, and remove the inclusion
of `log-patterns.c` from both.

spa/plugins/support/journal.c

@@ -39,12 +39,12 @@
 
 #include <systemd/sd-journal.h>
 
+#include "log-patterns.h"
+
 #define NAME "journal"
 
 #define DEFAULT_LOG_LEVEL SPA_LOG_LEVEL_INFO
 
-#include "log-patterns.c"
-
 struct impl {
 	struct spa_handle handle;
 	struct spa_log log;