ACPI: PM: Remove redundant cache flushing

ACPICA code takes care about cache flushing on S1/S2/S3 in
acpi_hw_extended_sleep() and acpi_hw_legacy_sleep().

acpi_suspend_enter() calls into ACPICA code via acpi_enter_sleep_state()
for S1 or x86_acpi_suspend_lowlevel() for S3.

acpi_sleep_prepare() call tree:
__acpi_pm_prepare()
acpi_pm_prepare()
acpi_suspend_ops::prepare_late()
acpi_hibernation_ops::pre_snapshot()
acpi_hibernation_ops::prepare()
acpi_suspend_begin_old()
acpi_suspend_begin_old::begin()
acpi_hibernation_begin_old()
acpi_hibernation_ops_old::acpi_hibernation_begin_old()
acpi_power_off_prepare()
pm_power_off_prepare()

Hibernation (S4) and Power Off (S5) don't require cache flushing, so
the only interesting callsites are acpi_suspend_ops::prepare_late()
and acpi_suspend_begin_old::begin(). Both of them have cache flush
on ->enter() operation in acpi_suspend_enter().

Remove redundant ACPI_FLUSH_CPU_CACHE() in acpi_sleep_prepare() and
acpi_suspend_enter().

Signed-off-by: Kirill A. Shutemov <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/sleep.c

···
 		acpi_set_waking_vector(acpi_wakeup_address);
 
 	}
-	ACPI_FLUSH_CPU_CACHE();
 #endif
 	pr_info("Preparing to enter system sleep state S%d\n", acpi_state);
 	acpi_enable_wakeup_devices(acpi_state);
···
 	acpi_status status = AE_OK;
 	u32 acpi_state = acpi_target_sleep_state;
 	int error;
-
-	ACPI_FLUSH_CPU_CACHE();
 
 	trace_suspend_resume(TPS("acpi_suspend"), acpi_state, true);
 	switch (acpi_state) {