soc/intel/quark: Add I2C support

Add the I2C driver.

TEST=Build and run on Galileo Gen2

Change-Id: I53fdac93667a8ffb2c2c8f394334de2dece63d66
Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-on: https://review.coreboot.org/14828
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/intel/quark/Makefile.inc

@@ -25,6 +25,7 @@ romstage-$(CONFIG_ENABLE_BUILTIN_HSUART1) += uart_common.c
 
 ramstage-$(CONFIG_HAVE_ACPI_TABLES) += acpi.c
 ramstage-y += chip.c
+ramstage-y += gpio_i2c.c
 ramstage-y += memmap.c
 ramstage-y += northcluster.c
 ramstage-y += pmc.c