x86, MCE, AMD: Move invariant code out from loop body

Assigning to mce_threshold_vector is loop-invariant code in
mce_amd_feature_init(). So do it only once, out of loop body.

Signed-off-by: Chen Yucong <slaoub@gmail.com>
Link: http://lkml.kernel.org/r/1412263212.8085.6.camel@debian
[ Boris: commit message corrections. ]
Signed-off-by: Borislav Petkov <bp@suse.de>

arch/x86/kernel/cpu/mcheck/mce_amd.c

@@ -253,7 +253,9 @@ void mce_amd_feature_init(struct cpuinfo_x86 *c)
 			}
 
 			mce_threshold_block_init(&b, offset);
-			mce_threshold_vector = amd_threshold_interrupt;
+
+			if (mce_threshold_vector != amd_threshold_interrupt)
+				mce_threshold_vector = amd_threshold_interrupt;
 		}
 	}
 }