haswell: Make `copy_spd` a weak function

Instead of using function pointers, we can use weak functions. So, drop
the pointer from `romstage_params`, leaving `pei_data` as the only
remaining member. This will be cleaned up in a follow-up commit.

Change-Id: I3b17d21ea7a650734119a5cab4892fcb158b589d
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43105
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/northbridge/intel/haswell/raminit.h b/src/northbridge/intel/haswell/raminit.h
index 562c24d..920ee0f 100644
--- a/src/northbridge/intel/haswell/raminit.h
+++ b/src/northbridge/intel/haswell/raminit.h
@@ -5,6 +5,9 @@
 
 #include "pei_data.h"
 
+/* Optional function to copy SPD data for on-board memory */
+void copy_spd(struct pei_data *peid);
+
 void sdram_initialize(struct pei_data *pei_data);
 void setup_sdram_meminfo(struct pei_data *pei_data);
 int fixup_haswell_errata(void);