sifive/hifive-unleashed: enable CBMEM support

Change-Id: I3eacba9c1c20bbfa270dd7a9afabe48ed9092bcc
Signed-off-by: Philipp Hug <philipp@hug.cx>
Reviewed-on: https://review.coreboot.org/28622
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/sifive/hifive-unleashed/romstage.c

@@ -42,5 +42,7 @@ void main(void)
 
 	sdram_init();
 
+	cbmem_initialize_empty();
+
 	run_ramstage();
 }

src/soc/sifive/fu540/Makefile.inc

@@ -21,6 +21,7 @@ bootblock-y += bootblock.c
 romstage-y += uart.c
 romstage-y += media.c
 romstage-y += sdram.c
+romstage-y += cbmem.c
 romstage-y += otp.c
 romstage-y += clock.c