Switch to fat32 file system for SD rom loading (nand2mario#27)

This removes the custom SD data format and switch to plain fat32 file system for rom loading.
Just place rom files in the root dir and the menu system should work as before.
Also use usb_hid_host for gamepad support.

nes.gprj

@@ -35,13 +35,14 @@
         <File path="src/nes2hdmi.sv" type="file.verilog" enable="1"/>
         <File path="src/nes_tang20k.v" type="file.verilog" enable="1"/>
         <File path="src/ppu.v" type="file.verilog" enable="1"/>
+        <File path="src/sd_file_list_reader.v" type="file.verilog" enable="1"/>
         <File path="src/sd_loader.v" type="file.verilog" enable="1"/>
         <File path="src/sd_reader.sv" type="file.verilog" enable="1"/>
         <File path="src/sdcmd_ctrl.sv" type="file.verilog" enable="1"/>
         <File path="src/sdram.v" type="file.verilog" enable="1"/>
         <File path="src/uart_tx_V2.v" type="file.verilog" enable="1"/>
-        <File path="src/usb_gamepad.v" type="file.verilog" enable="1"/>
-        <File path="src/usb_gamepad_rom.v" type="file.verilog" enable="1"/>
+        <File path="src/usb_hid_host.v" type="file.verilog" enable="1"/>
+        <File path="src/usb_hid_host_rom.v" type="file.verilog" enable="1"/>
         <File path="src/nestang.cst" type="file.cst" enable="1"/>
         <File path="src/nestang_dock.cst" type="file.cst" enable="0"/>
         <File path="src/nestang.sdc" type="file.sdc" enable="1"/>