sb/intel/*: Use common SMBus functions

All Intel southbridges implement the same SMBus functions.
This patch replaces all these similar and mostly identical
implementations with a common file.

This also makes i2c block read available to all those southbridges.
If the northbridge has to read a lot of SPD bytes sequentially, using
this function can reduce the time being spent to read SPD five-fold.

Change-Id: I93bb186e04e8c32dff04fc1abe4b5ecbc4c9c962
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/19258
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/northbridge/intel/sandybridge/raminit.c

@@ -25,7 +25,7 @@
 #include <timestamp.h>
 #include <northbridge/intel/common/mrc_cache.h>
 #include <southbridge/intel/bd82x6x/me.h>
-#include <southbridge/intel/bd82x6x/smbus.h>
+#include <southbridge/intel/common/smbus.h>
 #include <cpu/x86/msr.h>
 #include <delay.h>
 #include <smbios.h>