Revert "ACPI / LPSS: Remove non-existing clock control from Intel Lynxpoint I2C"

Revert commit b893e80e ("ACPI / LPSS: Remove non-existing clock control
from Intel Lynxpoint I2C") because it causes touchpad to not load on Dell
XPS13.

Regression is a clear indication that not only some early prototype version
of Lynxpoint I2C but also newer versions can be doing clock gating even
documentation does not state it.

Therefore it is best to revert since this clock gating haven't caused known
issues on those Lynxpoint version which don't do clock gating.
Reported-by-and-tested-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpi_lpss.c

@@ -125,7 +125,7 @@ static struct lpss_device_desc lpt_dev_desc = {
 };
 
 static struct lpss_device_desc lpt_i2c_dev_desc = {
-	.flags = LPSS_CLK | LPSS_LTR,
+	.flags = LPSS_CLK | LPSS_CLK_GATE | LPSS_LTR,
 	.prv_offset = 0x800,
 };