sh: earlyprintk= support and cleanups.

Allow multiple early printk consoles via earlyprintk=.

With this change earlyprintk is no longer enabled by default,
it must be specified on the kernel command line. Optionally
with ,keep to prevent unreg by tty_io.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

include/asm-sh/setup.h

@@ -4,5 +4,7 @@
 
 #define COMMAND_LINE_SIZE 256
 
+int setup_early_printk(char *);
+
 #endif /* _SH_SETUP_H */
 #endif /* __KERNEL__ */