riscv: Enable function sections

The linker can remove sections that are never addressed, so it makes a lot
of sense to declare every function as an individual section.

This reduces the output U-Boot code size by ~30kb for me.

Signed-off-by: Alexander Graf <agraf@suse.de>

arch/riscv/config.mk

@@ -29,5 +29,5 @@ 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
+PLATFORM_RELFLAGS += -fno-strict-aliasing -fno-common -gdwarf-2 -ffunction-sections
 LDFLAGS_u-boot += --gc-sections -static -pie