Make STANDALONE_LOAD_ADDR configurable per board

Rename STANDALONE_LOAD_ADDR into CONFIG_STANDALONE_LOAD_ADDR
and allow that the architecture-specific default value gets
overwritten by defining the value in the board header file.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
Cc: Daniel Hellstrom <daniel@gaisler.com>
Cc: Tsi Chung Liew <tsi-chung.liew@freescale.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/arch/avr32/config.mk b/arch/avr32/config.mk
index 1121ca1..9488c49 100644
--- a/arch/avr32/config.mk
+++ b/arch/avr32/config.mk
@@ -23,7 +23,7 @@
 
 CROSS_COMPILE ?= avr32-linux-
 
-STANDALONE_LOAD_ADDR = 0x00000000
+CONFIG_STANDALONE_LOAD_ADDR ?= 0x00000000
 
 PLATFORM_RELFLAGS	+= -ffixed-r5 -fPIC -mno-init-got -mrelax
 PLATFORM_LDFLAGS	+= --relax