config.mk: Remove duplicated -fno-strict-aliasing

Now that we already disable the "strict-aliasing" globally, remove
the duplicates in the nds32/riscv/x86 arch-specific Makefiles.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Rick Chen <rick@andestech.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/nds32/config.mk b/arch/nds32/config.mk
index cb3d8b3..c5520fd 100644
--- a/arch/nds32/config.mk
+++ b/arch/nds32/config.mk
@@ -15,7 +15,7 @@
 CONFIG_STANDALONE_LOAD_ADDR = 0x300000 \
 			      -T $(srctree)/examples/standalone/nds32.lds
 
-PLATFORM_RELFLAGS	+= -fno-strict-aliasing -fno-common -mrelax
+PLATFORM_RELFLAGS	+= -fno-common -mrelax
 PLATFORM_RELFLAGS	+= -gdwarf-2
 PLATFORM_CPPFLAGS	+= -D__nds32__ -G0 -ffixed-10 -fpie