Added riscv_core top level file containing only the interface.

sources/riscv_core.vhd

+library work;
+use work.riscv_pkg.all;
+
+entity riscv_core is
+    port (
+    i_rstn : in std_logic;
+    i_clk : in std_logic;
+    o_imem_en : out std_logic;
+    o_imem_addr : out std_logic_vector(8 downto 0);
+    i_imem_read : in std_logic_vector(31 downto 0);
+    o_dmem_en : out std_logic;
+    o_dmem_we : out std_logic;
+    o_dmem_addr : out std_logic_vector(8 downto 0);
+    i_dmem_read : in std_logic_vector(31 downto 0);
+    o_dmem_write : out std_logic_vector(31 downto 0);
+    -- DFT
+    i_scan_en : in std_logic;
+    i_test_mode : in std_logic;
+    i_tdi : in std_logic;
+    o_tdo : out std_logic);
+end entity riscv_core;
+
+architecture beh of riscv_core is
+end architecture beh;