Add a soft-float riscv kernel config

GENERICSF is just like GENERIC, only creates a soft-float kernel. Omit it from the
universe build for now.

Reviewed by: philip
Differential Revision: https://reviews.freebsd.org/D23812

sys/conf/Makefile.riscv

@@ -19,7 +19,7 @@
 #
 
 # Which version of config(8) is required.
-%VERSREQ=	600012
+%VERSREQ=	600017
 
 .if !defined(S)
 S=	../../..

sys/conf/kern.mk

@@ -306,4 +306,5 @@ LD_EMULATION_powerpc= elf32ppc_fbsd
 LD_EMULATION_powerpcspe= elf32ppc_fbsd
 LD_EMULATION_powerpc64= elf64ppc_fbsd
 LD_EMULATION_riscv64= elf64lriscv
+LD_EMULATION_riscv64sf= elf64lriscv
 LD_EMULATION=${LD_EMULATION_${MACHINE_ARCH}}

sys/riscv/conf/GENERICSF

@@ -0,0 +1,9 @@
+# $FreeBSD$
+
+# Just like generic, but with a riscv64sf MACHINE_ARCH. Override machine set in
+# DEFAULTS.
+machine riscv riscv64sf
+
+include		"GENERIC"
+ident		GENERICSF
+nooptions	FPE			# for systems without FPE