skylake: Support for early I2C TPM driver

Add the SOC definition for acpi_get_gpe() so it can be used
by the I2C TPM driver.  Also add the I2C support code to
verstage so it can get used by vboot.

BUG=chrome-os-partner:58666
TEST=boot with I2C TPM on skylake board

Change-Id: I553f00a6ec25955ecc18a7616d9c3e1e7cbbb8ca
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/17136
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
diff --git a/src/soc/intel/skylake/pmutil.c b/src/soc/intel/skylake/pmutil.c
index 31de242..904be5c 100644
--- a/src/soc/intel/skylake/pmutil.c
+++ b/src/soc/intel/skylake/pmutil.c
@@ -351,6 +351,26 @@
 				gpe0_sts_3_bits);
 }
 
+/* Read and clear GPE status (defined in arch/acpi.h) */
+int acpi_get_gpe(int gpe)
+{
+	int bank;
+	uint32_t mask, sts;
+
+	if (gpe < 0 || gpe > GPE0_WADT)
+		return -1;
+
+	bank = gpe / 32;
+	mask = 1 << (gpe % 32);
+
+	sts = inl(ACPI_BASE_ADDRESS + GPE0_STS(bank));
+	if (sts & mask) {
+		outl(mask, ACPI_BASE_ADDRESS + GPE0_STS(bank));
+		return 1;
+	}
+	return 0;
+}
+
 /* Enable all requested GPE */
 void enable_all_gpe(u32 set1, u32 set2, u32 set3, u32 set4)
 {