ppc/85xx: Introduce RESET_VECTOR_ADDRESS to handle non-standard link address

Some board ports place TEXT_BASE at a location that would cause the
RESET_VECTOR_ADDRESS not to be at 0xfffffffc when we link.  By default
we assume RESET_VECTOR_ADDRESS will be 0xfffffffc if the board doesn't
explicitly set it.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Wolfgang Denk <wd@denx.de>
diff --git a/board/freescale/mpc8572ds/config.mk b/board/freescale/mpc8572ds/config.mk
index 08b61f0..67394c9 100644
--- a/board/freescale/mpc8572ds/config.mk
+++ b/board/freescale/mpc8572ds/config.mk
@@ -26,3 +26,5 @@
 ifndef TEXT_BASE
 TEXT_BASE = 0xeff80000
 endif
+
+RESET_VECTOR_ADDRESS = 0xeffffffc