m68k: mac: Improve IOP debug messages

Always dump the full message and reply. Avoid printing partial lines
as this output gets mixed up with the output from called functions.
Don't output the state of idle channels.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Stan Johnson <userm57@yahoo.com>
Cc: Joshua Thompson <funaho@jurai.org>
Link: https://lore.kernel.org/r/317909d69244f06581973c5839382f5516cd9a1c.1590880333.git.fthain@telegraphics.com.au


Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>