platform / x86 / PM: Fix unused function warnings for CONFIG_PM_SLEEP

According to compiler warnings, quite some suspend/resume functions
in platform x86 drivers are not used for CONFIG_PM_SLEEP unset, so
add #ifdefs to prevent them from being built in that case.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
diff --git a/drivers/platform/x86/fujitsu-tablet.c b/drivers/platform/x86/fujitsu-tablet.c
index d2e4173..7acae3f 100644
--- a/drivers/platform/x86/fujitsu-tablet.c
+++ b/drivers/platform/x86/fujitsu-tablet.c
@@ -440,11 +440,13 @@
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
 static int acpi_fujitsu_resume(struct device *dev)
 {
 	fujitsu_reset();
 	return 0;
 }
+#endif
 
 static SIMPLE_DEV_PM_OPS(acpi_fujitsu_pm, NULL, acpi_fujitsu_resume);