arch/riscv: Refactor bootblock.S

A few things are currently missing:
- The trap handler doesn't set the stack pointer, which can easily
  result in trap loops or memory corruptions.
- The SBI trampolin page (as described in version 1.9 of the RISC-V
  Privileged Architecture Specification), has been removed for now.

Change-Id: Id89c859fab354501c94a0e82d349349c29fa4cc6
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/15591
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
diff --git a/src/arch/riscv/id.S b/src/arch/riscv/id.S
new file mode 100644
index 0000000..798aa89
--- /dev/null
+++ b/src/arch/riscv/id.S
@@ -0,0 +1,33 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * This program 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; version 2 of the License.
+ *
+ * This program 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.
+ */
+
+#include <build.h>
+
+	.section ".id", "a", %progbits
+
+	.globl __id_start
+__id_start:
+ver:
+	.asciz "1" //COREBOOT_VERSION
+vendor:
+	.asciz "ucb" //CONFIG_MAINBOARD_VENDOR
+part:
+	.asciz "1" //CONFIG_MAINBOARD_PART_NUMBER
+.long __id_end + CONFIG_ID_SECTION_OFFSET - ver  /* Reverse offset to the vendor id */
+.long __id_end + CONFIG_ID_SECTION_OFFSET - vendor  /* Reverse offset to the vendor id */
+.long __id_end + CONFIG_ID_SECTION_OFFSET - part    /* Reverse offset to the part number */
+.long CONFIG_ROM_SIZE                               /* Size of this romimage */
+	.globl __id_end
+
+__id_end:
+.previous