m68k/mac: early console

Revive the old mac_serial_print() routine as mac_early_print(). mac_serial_print() did not function because it did not use the right offsets for its stack arguments. Fix this and make compilation conditional on CONFIG_EARLY_PRINTK instead of the obscure MAC_SERIAL_DEBUG macro.

Give mac_early_print() a new string length parameter to fit the early console API.

Send output to the framebuffer as well as serial ports.

Change the line rate to 38400 baud to match the default for the real (pmac_zilog) serial console.

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