serial: isicom.c: use pr_fmt and pr_<level>

Add #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
Convert printks to pr_<level>
Convert some embedded function names to %s...__func__
Remove a period after exclamation points.
Remove #define pr_dbg which could be used by future kernel.h includes

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>