m68k/mac: Modernize printing of kernel messages

Convert from printk() to pr_*().

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
[FT: Adjusted log message severity levels and retained bootinfo log]
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>