m68k: remove CONFIG_EARLY_PRINTK dependency on CONFIG_EMBEDDED, default to n

Allow CONFIG_EARLY_PRINTK without requiring both CONFIG_EMBEDDED and
CONFIG_DEBUG. Default to disabled.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>