syslog: add an option to completely disable syslog logic

Add an option to completely disable syslog() and replace it with an empty functions.
This option can be useful for small systems when we don't have any logging support,
but compiler is not able to remove useless code.

This way the final image also won't contain the strings that are present in
syslog() calls when compiler optimization is enabled (for example from /boards
where syslog is often used instead of debug macros).

Signed-off-by: raiden00pl <raiden00@railab.me>

libs/libc/syslog/Make.defs

@@ -26,6 +26,10 @@ ifeq ($(CONFIG_SYSLOG),y)
 CSRCS += lib_syslog.c lib_setlogmask.c
 endif
 
+ifeq ($(CONFIG_SYSLOG_NONE),y)
+CSRCS += lib_syslog_none.c
+endif
+
 # Add the syslog directory to the build
 
 DEPPATH += --dep-path syslog