ddr3 spd: move accessor code into lib/spd_bin.c

It's an attempt to consolidate the access code, even if there are still
multiple implementations in the code.

Change-Id: I4b2b9cbc24a445f8fa4e0148f52fd15950535240
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: https://review.coreboot.org/18265
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/device/Kconfig

@@ -210,10 +210,6 @@ config SMBUS_HAS_AUX_CHANNELS
 	bool
 	default n
 
-config SPD_CACHE
-	bool
-	default n
-
 config PCI
 	bool
 	default n