soc/intel/quark: Split I2C out from driver

Split out the I2C code to allow I2C transactions during early romstage.

TEST=Build and run on Galileo Gen2

Change-Id: I87ceb0a8cf660e4337738b3bcde9d4fdeae0159d
Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-on: https://review.coreboot.org/15007
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/intel/quark/Makefile.inc

@@ -18,6 +18,7 @@ ifeq ($(CONFIG_SOC_INTEL_QUARK),y)
 subdirs-y += romstage
 subdirs-y += ../../../cpu/x86/tsc
 
+romstage-y += i2c.c
 romstage-y += memmap.c
 romstage-y += reg_access.c
 romstage-y += tsc_freq.c
@@ -27,6 +28,7 @@ ramstage-$(CONFIG_HAVE_ACPI_TABLES) += acpi.c
 ramstage-y += chip.c
 ramstage-y += ehci.c
 ramstage-y += gpio_i2c.c
+ramstage-y += i2c.c
 ramstage-y += lpc.c
 ramstage-y += memmap.c
 ramstage-y += northcluster.c