cpu/x86: Rename __protected_start symbol

It was confusing to have this defined while there was another
symbol bootblock_protected_mode_entry that was not really used
as an entry point.

Change-Id: I3da07ba9c0a9fc15b1515452adfb27f963659951
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48404
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-by: Jason Glenesk <jason.glenesk@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/amd/common/block/cpu/noncar/pre_c.S b/src/soc/amd/common/block/cpu/noncar/pre_c.S
index 520e3c0..5c16c29 100644
--- a/src/soc/amd/common/block/cpu/noncar/pre_c.S
+++ b/src/soc/amd/common/block/cpu/noncar/pre_c.S
@@ -18,7 +18,7 @@
 /*
  * on entry:
  *   mm0: BIST (ignored)
- *   mm2_mm1: timestamp at bootblock_protected_mode_entry
+ *   mm2_mm1: timestamp
  */
 
 .global bootblock_pre_c_entry