Correct "MTTR" to "MTRR"

The term MTRR has been misspelled in a few places.

Change-Id: I3e3c11f80de331fa45ae89779f2b8a74a0097c74
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/25568
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/drivers/intel/fsp1_1/stack.c

@@ -36,7 +36,7 @@ void *setup_stack_and_mtrrs(void)
 	uint32_t num_mtrrs;
 	uint32_t *slot;
 
-	/* Display the MTTRs */
+	/* Display the MTRRs */
 	soc_display_mtrrs();
 
 	/* Top of stack needs to be aligned to a 8-byte boundary. */