ACPI: bus: Use pr_*() macros to replace printk()

In commit ee98460b ("ACPI: bus: Clean up printing messages"),
direct printk() invocations was replaced with the matching pr_*()
calls, but the left two printk() calls was merged at the same time
with the above cleaup commit, so we missed them for cleanup, let's
replace them now and we can remove the use of PREFIX later.

Signed-off-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>