RISC-V: Add auxiliary files

To support a new architecture we need to provide a few helper functions
for memory, cache, timer, etc support.

This patch adds the remainders of those. Some bits are still disabled,
as I couldn't guarantee that we're always running on models / in modes
where the respective hardware is available.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/kern/riscv/cache_flush.S

@@ -0,0 +1,44 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2018  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/symbol.h>
+
+	.file	"cache_flush.S"
+	.text
+
+/*
+ * Simple cache maintenance functions
+ */
+
+/*
+ * a0 - *beg (inclusive)
+ * a1 - *end (exclusive)
+ * a2 - line size
+*/
+FUNCTION(grub_arch_clean_dcache_range)
+	/* TODO */
+	ret
+
+/*
+ * a0 - *beg (inclusive)
+ * a1 - *end (exclusive)
+ * a2 - line size
+ */
+FUNCTION(grub_arch_invalidate_icache_range)
+	fence.i
+	ret