KVM: PPC: Use seq_puts() in kvmppc_exit_timing_show()

A headline should be quickly put into a sequence. Thus use the
function "seq_puts" instead of "seq_printf" for this purpose.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>