riscv: Remove MACHINE_ARCH-specific remnants of riscv64sf.

- Remove now unnecessary MACHINE_ARCHES definition.  The default logic
  in kern_mib.c works fine now for RISC-V.

- Remove custom sv_machine_arch hook from sysentvec.

Fixes:		1ca12bd927 Remove the riscv64sf architecture.
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D40648

sys/riscv/include/param.h

@@ -50,9 +50,6 @@
 #ifndef MACHINE_ARCH
 #define	MACHINE_ARCH	"riscv64"
 #endif
-#ifdef _KERNEL
-#define	MACHINE_ARCHES	"riscv64"
-#endif
 
 #ifdef SMP
 #ifndef MAXCPU

sys/riscv/riscv/elf_machdep.c

@@ -59,8 +59,6 @@ __FBSDID("$FreeBSD$");
 #include <machine/elf.h>
 #include <machine/md_var.h>
 
-static const char *riscv_machine_arch(struct proc *p);
-
 u_long elf_hwcap;
 
 static struct sysentvec elf64_freebsd_sysvec = {
@@ -98,7 +96,6 @@ static struct sysentvec elf64_freebsd_sysvec = {
 	.sv_thread_detach = NULL,
 	.sv_trap	= NULL,
 	.sv_hwcap	= &elf_hwcap,
-	.sv_machine_arch = riscv_machine_arch,
 	.sv_onexec_old	= exec_onexec_old,
 	.sv_onexit	= exit_onexit,
 	.sv_regset_begin = SET_BEGIN(__elfN(regset)),
@@ -106,16 +103,6 @@ static struct sysentvec elf64_freebsd_sysvec = {
 };
 INIT_SYSENTVEC(elf64_sysvec, &elf64_freebsd_sysvec);
 
-static const char *
-riscv_machine_arch(struct proc *p)
-{
-
-	if ((p->p_elf_flags & EF_RISCV_FLOAT_ABI_MASK) ==
-	    EF_RISCV_FLOAT_ABI_SOFT)
-		return (MACHINE_ARCH "sf");
-	return (MACHINE_ARCH);
-}
-
 static Elf64_Brandinfo freebsd_brand_info = {
 	.brand		= ELFOSABI_FREEBSD,
 	.machine	= EM_RISCV,