clocksource, acpi_pm.c: put acpi_pm_read_slow() under CONFIG_PCI

acpi_pm_read_slow() is only used when CONFIG_PCI=y, so move the definition
inside the ifdef.

Otherwise this causes a "defined but not used" warning when building with
CONFIG_ACPI=y and CONFIG_PCI=n (that's not supported yet, but it could
be).

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: mingo@elte.hu
Cc: johnstul@us.ibm.com
Cc: akpm@linux-foundation.org
Cc: bjorn.helgaas@hp.com
Cc: lenb@kernel.org
Cc: linux@dominikbrodowski.net
Cc: tglx@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/clocksource/acpi_pm.c

@@ -57,11 +57,6 @@ u32 acpi_pm_read_verified(void)
 	return v2;
 }
 
-static cycle_t acpi_pm_read_slow(void)
-{
-	return (cycle_t)acpi_pm_read_verified();
-}
-
 static cycle_t acpi_pm_read(void)
 {
 	return (cycle_t)read_pmtmr();
@@ -88,6 +83,11 @@ static int __init acpi_pm_good_setup(char *__str)
 }
 __setup("acpi_pm_good", acpi_pm_good_setup);
 
+static cycle_t acpi_pm_read_slow(void)
+{
+	return (cycle_t)acpi_pm_read_verified();
+}
+
 static inline void acpi_pm_need_workaround(void)
 {
 	clocksource_acpi_pm.read = acpi_pm_read_slow;