kconfig: delete redundant CONFIG_${ARCH} definition

CONFIG_${ARCH} is defined by Kconfig.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/openrisc/config.mk b/arch/openrisc/config.mk
index 9902b9a..cd95f24 100644
--- a/arch/openrisc/config.mk
+++ b/arch/openrisc/config.mk
@@ -11,6 +11,6 @@
 
 # r10 used for global object pointer, already set in OR32 GCC but just to be
 # clear
-PLATFORM_CPPFLAGS += -DCONFIG_OPENRISC -D__OR1K__ -ffixed-r10
+PLATFORM_CPPFLAGS += -D__OR1K__ -ffixed-r10
 
 CONFIG_STANDALONE_LOAD_ADDR ?= 0x40000