arch: blackfin: kernel: setup.c: Cleaning up missing null-terminate in conjunction with strncpy

Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Steven Miao <realmz6@gmail.com>

arch/blackfin/kernel/setup.c

@@ -1464,5 +1464,5 @@ void __init cmdline_init(const char *r0)
 {
 	early_shadow_stamp();
 	if (r0)
-		strncpy(command_line, r0, COMMAND_LINE_SIZE);
+		strlcpy(command_line, r0, COMMAND_LINE_SIZE);
 }