ddr3 spd: Rename read_spd_from_cbfs() to read_ddr3_spd_from_cbfs()

Since it checks for DDR3 style checksums, it's a more appropriate name.
Also make its configuration local for a future code move.

Change-Id: I417ae165579618d9215b8ca5f0500ff9a61af42f
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: https://review.coreboot.org/18264
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

src/include/spd_cache.h

@@ -18,9 +18,9 @@
 #include <stdint.h>
 
 #if IS_ENABLED(CONFIG_SPD_CACHE)
-int read_spd_from_cbfs(u8 *buf, int idx);
+int read_ddr3_spd_from_cbfs(u8 *buf, int idx);
 #else
-static inline int read_spd_from_cbfs(u8 *buf, int idx) { return -1; }
+static inline int read_ddr3_spd_from_cbfs(u8 *buf, int idx) { return -1; }
 #endif
 
 #endif