cpu/intel/common: rework AES-NI locking

Simplify the AES-NI code by using msr_set and correct the comment.

Change-Id: Ib2cda433bbec0192277839c02a1862b8f41340cb
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46275
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/cpu/intel/common/common.h

@@ -28,8 +28,8 @@ bool intel_ht_supported(void);
 bool intel_ht_sibling(void);
 
 /*
- * Lock AES-NI feature (MSR_FEATURE_CONFIG) to prevent unintended disabling
- * as suggested in Intel document 325384-070US.
+ * Lock AES-NI feature (MSR_FEATURE_CONFIG) to prevent unintended changes
+ * to the enablement state as suggested in Intel document 325384-070US.
  */
 void set_aesni_lock(void);