boardid: Minor clean up and standardization

Merge the different coreboot table strapping ID structures into one
because they're really just all the same, and I want to add more. Make
the signature of the board_id() function return a uint32_t because
that's also what goes in the coreboot table. Add a printk to the generic
code handling strapping IDs in ramstage so that not every individual
mainboard implementation needs its own print. (In turn, remove one such
print from fsp1_1 code because it's in the way of my next patch.)

Change-Id: Ib9563edf07b623a586a4dc168fe357564c5e68b5
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/22741
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/boardid.h

@@ -18,7 +18,9 @@
 
 #include <stdint.h>
 
-uint8_t board_id(void);
+#define UNDEFINED_STRAPPING_ID (~0)
+
+uint32_t board_id(void);
 uint32_t ram_code(void);
 
 #endif /* __INCLUDE_BOARDID_H__ */