powerpc/xics: Make printk format strings fit on one line

Several printks were broken at word boundaries for line length.   Some
even referred to old function names.   Using __func__ and changing the
text slightly for the format allows these printk formats to fit on one
line.

Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>