cpu/intel/haswell: Set C9/C10 vccmin

Backport commit ab7586fa26 (broadwell: Set C9/C10 vccmin) to Haswell.

Change-Id: I9cddc7dd45e96c6f99327ee2583917bf8bedfbdd
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46922
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/northbridge/intel/haswell/registers/mchbar.h b/src/northbridge/intel/haswell/registers/mchbar.h
index 4bdb49a..a61036a 100644
--- a/src/northbridge/intel/haswell/registers/mchbar.h
+++ b/src/northbridge/intel/haswell/registers/mchbar.h
@@ -46,6 +46,9 @@
 #define  MAILBOX_BIOS_CMD_FSM_MEASURE_INTVL	0x909
 #define  MAILBOX_BIOS_CMD_READ_PCH_POWER	0xa
 #define  MAILBOX_BIOS_CMD_READ_PCH_POWER_EXT	0xb
+#define  MAILBOX_BIOS_CMD_READ_C9C10_VOLTAGE	0x26
+#define  MAILBOX_BIOS_CMD_WRITE_C9C10_VOLTAGE	0x27
+
 /* Errors are returned back in bits 7:0 */
 #define  MAILBOX_BIOS_ERROR_NONE		0
 #define  MAILBOX_BIOS_ERROR_INVALID_COMMAND	1