skylake: remove ec_smi_gpio and alt_gp_smi_en

The ec_smi_gpio and alt_gp_smi_en devicetree options are
goign to be removed. The plan for skylake is to set the
settings by the mainboard through either gpio pad
configuration or through helper functions.

Moreover, these values only allow *1* SMI GPIO configuration
in that the following has to be true:
alt_gp_smi_en = 1 << (ec_smi_gpio % 24)
If not, then another gpio(s) from the same group has the
SMI_EN bit set for it.

Lastly, remove all the subsequent dependencies as they are
no longer used: enable_alt_smi() and gpio_enable_group().

BUG=chrome-os-partner:43778
BRANCH=None
TEST=None

Original-Change-Id: I749a499c810d83de522a2ccce1dd9efb0ad2e20a
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/291931
Original-Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

Change-Id: I2e1cd6879b76923157268a1449c617ef2aada9c4
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/11204
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/soc/intel/skylake/pmutil.c

@@ -258,14 +258,6 @@ u32 clear_alt_smi_status(void)
 	return print_alt_smi_status();
 }
 
-/* Enable GPIO SMI events */
-void enable_alt_smi(int gpionum, u32 mask)
-{
-	/*Set GPIO EN Status*/
-	gpio_enable_groupsmi(gpionum, mask);
-}
-
-
 /*
  * TCO
  */