am335x: Add the config variable ROMSTAGE_BASE to the CPU's Kconfig.

This variable wasn't being defined and was defaulting to zero when used in the
ROM stage's linker script. This change defines it as a variable, and gives it
a value which is slightly beyond the end of the bootblock. By making the ROM
stage request to be loaded slightly farther into memory than it was loaded by
the SOC's masked ROM, we ensure that it's moved away from the stage's metadata
instead of on top of it. When it moves the other way, it clobbers important
values like the entry point vefore the bootblock has had a chance to use them.

Change-Id: I027a1365d05f1d79d7fc1e1349965ccb7d4e81b9
Signed-off-by: Gabe Black <gabeblack@chromium.org>
Reviewed-on: http://review.coreboot.org/3582
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/cpu/ti/am335x/Kconfig

@@ -10,6 +10,17 @@ config BOOTBLOCK_BASE
 	hex
 	default 0x402f0400
 
+config CBFS_ROM_OFFSET
+	# Calculated by BL1 + max bootblock size.
+	default 0x4c00
+
+# We need to leave a gap between the bootblock and the ROM stage so that when
+# it is "loaded" to a slightly different place in on chip memory, it doesn't
+# clobber the metadata needed to actually enter it.
+config ROMSTAGE_BASE
+	hex
+	default 0x402f5400
+
 # Stack may reside in either IRAM or DRAM. We will define it to live
 # at the top of IRAM for now.
 #
@@ -27,11 +38,6 @@ config STACK_SIZE
 	hex
 	default 0x1000
 
-config CBFS_ROM_OFFSET
-	# Calculated by BL1 + max bootblock size.
-	hex "offset of CBFS data in ROM"
-	default 0x2800
-
 ## TODO Change this to some better address not overlapping bootblock when
 ## cbfstool supports creating header in arbitrary location.
 config CBFS_HEADER_ROM_OFFSET