powerpc/setup: Adjust six seq_printf() calls in show_cpuinfo()

A bit of information should be put into a sequence.
Thus improve the execution speed for this data output by better usage
of corresponding functions.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/5b62379e-a35f-4f56-f1b5-6350f76007e7@web.de