nb/intel/sandybridge: Rename and clean up `discover_edges_write`

This is actually an (incomplete) aggressive read training algorithm.
Rename functions and variables accordingly, and tidy up declarations.

Tested on Asus P8H61-M PRO, still boots.

Change-Id: I8a4900f8e3acffe4e4d75a51a2588ad6b65eb411
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47679
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/src/northbridge/intel/sandybridge/raminit_native.c b/src/northbridge/intel/sandybridge/raminit_native.c
index ae9a4f4..eecd938 100644
--- a/src/northbridge/intel/sandybridge/raminit_native.c
+++ b/src/northbridge/intel/sandybridge/raminit_native.c
@@ -702,7 +702,7 @@
 
 		printram("CP5c\n");
 
-		err = discover_edges_write(ctrl);
+		err = aggressive_read_training(ctrl);
 		if (err)
 			return err;