cpu/intel: Add int to unsigned

Fix the following warning detected by checkpatch.pl:

WARNING: Prefer 'unsigned int' to bare use of 'unsigned'

TEST=Build and run on Galileo Gen2

Change-Id: I207713a3370e5a9abed4535187aa2aaeef502d6f
Signed-off-by: Lee Leahy <Leroy.P.Leahy@intel.com>
Reviewed-on: https://review.coreboot.org/18848
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/cpu/intel/model_206ax/bootblock.c

@@ -31,8 +31,8 @@
 #error "CPU must be paired with Intel BD82X6X or C216 southbridge"
 #endif
 
-static void set_var_mtrr(
-	unsigned reg, unsigned base, unsigned size, unsigned type)
+static void set_var_mtrr(unsigned int reg, unsigned int base, unsigned int size,
+	unsigned int type)
 
 {
 	/* Bit Bit 32-35 of MTRRphysMask should be set to 1 */