configs: Drop '$(ARCH)' usage in CONFIG_SPL_LDSCRIPT

In a few boards we had overridden, intentionally, the value used for
CONFIG_SPL_LDSCRIPT.  However, rather than using the ARCH value (arm)
they used the $(ARCH) variable in make.  This doesn't help really, so
switch to a hard-coded value.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/brppt2_defconfig b/configs/brppt2_defconfig
index f94ea28..4fde3b9 100644
--- a/configs/brppt2_defconfig
+++ b/configs/brppt2_defconfig
@@ -2,7 +2,7 @@
 # CONFIG_SPL_SYS_THUMB_BUILD is not set
 CONFIG_SYS_L2CACHE_OFF=y
 CONFIG_ARCH_MX6=y
-CONFIG_SPL_LDSCRIPT="arch/$(ARCH)/cpu/u-boot-spl.lds"
+CONFIG_SPL_LDSCRIPT="arch/arm/cpu/u-boot-spl.lds"
 CONFIG_SYS_TEXT_BASE=0x17800000
 CONFIG_SPL_GPIO_SUPPORT=y
 CONFIG_SPL_LIBCOMMON_SUPPORT=y