Add target_data_bits().

This is used to compute memory block read alignment, and specifically
allows 64-bit targets to ensure that memory block reads are only
requested on 64-bit boundaries.

Signed-off-by: Tim Newsome <tim@sifive.com>
Change-Id: Idb1a27b9fc02c46245556bb0f3d6d94b368c4817
Reviewed-on: http://openocd.zylin.com/6249
Reviewed-by: Marc Schink <dev@zapb.de>
Tested-by: jenkins
Reviewed-by: Jan Matyas <matyas@codasip.com>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/target/riscv/riscv.c

@@ -2813,6 +2813,14 @@ static unsigned riscv_xlen_nonconst(struct target *target)
 	return riscv_xlen(target);
 }
 
+static unsigned int riscv_data_bits(struct target *target)
+{
+	RISCV_INFO(r);
+	if (r->data_bits)
+		return r->data_bits(target);
+	return riscv_xlen(target);
+}
+
 struct target_type riscv_target = {
 	.name = "riscv",
 
@@ -2857,6 +2865,7 @@ struct target_type riscv_target = {
 	.commands = riscv_command_handlers,
 
 	.address_bits = riscv_xlen_nonconst,
+	.data_bits = riscv_data_bits
 };
 
 /*** RISC-V Interface ***/