tools/power turbostat: fix error case overflow read of slm_freq_table[]

When i >= SLM_BCLK_FREQS, the frequency read from the slm_freq_table
is off the end of the array because msr is set to 3 rather than the
actual array index i.  Set i to 3 rather than msr to fix this.
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

tools/power/x86/turbostat/turbostat.c

@@ -3036,7 +3036,7 @@ double slm_bclk(void)
 	i = msr & 0xf;
 	if (i >= SLM_BCLK_FREQS) {
 		fprintf(outf, "SLM BCLK[%d] invalid\n", i);
-		msr = 3;
+		i = 3;
 	}
 	freq = slm_freq_table[i];