m68k: Remove CONSOLE_PENGUIN macro, adopt CONFIG_LOGO

Allow CONFIG_LOGO to enable/disable the head.S penguin logo as well as the
framebuffer console logo. This should save a few bytes. It also gets rid
of the obscure CONSOLE_PENGUIN macro.

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