amd/stoneyridge: Use defined value for SPI flash MTRR

Replace an absolute value with a #define value in bootblock.  This is
in preparation for using an additional MTRR in a subsequent patch.

Change-Id: I006c7cfa0057b3ed4a21359fc8367caf6ec5baf3
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/25455
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Richard Spiegel <richard.spiegel@silverbackltd.com>

src/soc/amd/stoneyridge/bootblock/bootblock.c

@@ -25,6 +25,7 @@
 #include <amdblocks/agesawrapper.h>
 #include <amdblocks/agesawrapper_call.h>
 #include <soc/pci_devs.h>
+#include <soc/cpu.h>
 #include <soc/northbridge.h>
 #include <soc/southbridge.h>
 #include <amdblocks/psp.h>
@@ -61,7 +62,7 @@ static void amd_initmmio(void)
 	 * todo: AGESA currently writes variable MTRRs.  Once that is
 	 *       corrected, un-hardcode this MTRR.
 	 */
-	mtrr = (mtrr_cap.lo & MTRR_CAP_VCNT) - 2;
+	mtrr = (mtrr_cap.lo & MTRR_CAP_VCNT) - SOC_EARLY_VMTRR_FLASH;
 	set_var_mtrr(mtrr, FLASH_BASE_ADDR, CONFIG_ROM_SIZE, MTRR_TYPE_WRPROT);
 }
 

src/soc/amd/stoneyridge/include/soc/cpu.h

@@ -16,6 +16,17 @@
 #ifndef __STONEYRIDGE_CPU_H__
 #define __STONEYRIDGE_CPU_H__
 
+#include <device/device.h>
+
+/*
+ *  Set a variable MTRR in bootblock and/or romstage.  AGESA will use the lowest
+ *  numbered registers.  Any values defined below are subtracted from the
+ *  highest numbered registers.
+ *
+ *  todo: Revisit this once AGESA no longer programs MTRRs.
+ */
+#define SOC_EARLY_VMTRR_FLASH 2
+
 void stoney_init_cpus(struct device *dev);
 
 #endif /* __STONEYRIDGE_CPU_H__ */