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>

arch/riscv/config.mk

@@ -31,7 +31,7 @@ CONFIG_STANDALONE_LOAD_ADDR = 0x00000000 \
 			      -T $(srctree)/examples/standalone/riscv.lds
 
 PLATFORM_CPPFLAGS	+= -ffixed-gp -fpic
-PLATFORM_RELFLAGS += -fno-strict-aliasing -fno-common -gdwarf-2 -ffunction-sections
+PLATFORM_RELFLAGS += -fno-common -gdwarf-2 -ffunction-sections
 LDFLAGS_u-boot += --gc-sections -static -pie
 
 EFI_CRT0		:= crt0_riscv_efi.o