arch/riscv/Makefile.mk: Fix OpenSBI compilation

1. romstage.S should only be included if we have a separate romstage
2. FW_JUMP and FW_DYNAMIC are opposing options and we only support
   FW_DYNAMIC

Signed-off-by: Maximilian Brune <maximilian.brune@9elements.com>
Change-Id: Ic14fa77d2f223664b9faba048b759e03efffcde8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79952
Reviewed-by: Philipp Hug <philipp@hug.cx>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/src/arch/riscv/Makefile.mk b/src/arch/riscv/Makefile.mk
index bbd3959..1267195 100644
--- a/src/arch/riscv/Makefile.mk
+++ b/src/arch/riscv/Makefile.mk
@@ -96,7 +96,7 @@
 ################################################################################
 ifeq ($(CONFIG_ARCH_ROMSTAGE_RISCV),y)
 
-romstage-y += romstage.S
+romstage-$(CONFIG_SEPARATE_ROMSTAGE) += romstage.S
 
 # Build the romstage
 
@@ -163,10 +163,9 @@
 		AR="$(AR_ramstage)" \
 		PLATFORM=$(CONFIG_OPENSBI_PLATFORM) \
 		O="$(OPENSBI_BUILD)" \
-		FW_JUMP=y \
+		FW_JUMP=n \
 		FW_DYNAMIC=y \
 		FW_PAYLOAD=n \
-		FW_PAYLOAD_OFFSET=0 \
 		FW_TEXT_START=$(CONFIG_OPENSBI_TEXT_START)
 
 $(OPENSBI): $(OPENSBI_TARGET)