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/include/cpu/intel/msr.h

@@ -6,6 +6,6 @@
  */
 
 #define MSR_FEATURE_CONFIG	0x13c
-#define  AESNI_LOCK_BIT		0
+#define  AESNI_LOCK		(1 << 0)
 
 #endif /* CPU_INTEL_MSR_H */