msd: Remove legacy msd/start4.elf and use a common legacy msd .elf file

The legacy VPU firmware MSD drivers are deprecated on CM4 / Pi4.
Remove this but link to a generic legacy VPU MSD firmware which
supports 2711 and earlier chips.

N.B. mass-storage-gadget64-cm3 implements same functionality as the
Linux mass-storage-gadget. The only difference is in how the files
are loaded because older boards don't support a bootloader ramdisk.

To run the legacy VPU msd firmware on 2711 run
sudo rpiboot -d ./msd

Author: timg236

Makefile

@@ -5,7 +5,7 @@ GIT_VER=$(shell git rev-parse HEAD 2>/dev/null | cut -c1-8 || echo "")
 HAVE_XXD=$(shell xxd -v >/dev/null 2>/dev/null && echo y)
 INSTALL_PREFIX?=/usr
 
-rpiboot: main.c bootfiles.c decode_duid.c msd/bootcode.h msd/start.h msd/bootcode4.h msd/start4.h
+rpiboot: main.c bootfiles.c decode_duid.c msd/bootcode.h msd/start.h msd/bootcode4.h
 	$(CC) -Wall -Wextra -g $(CPPFLAGS) $(CFLAGS) -o $@ main.c bootfiles.c decode_duid.c `pkg-config --cflags --libs libusb-1.0` -DGIT_VER="\"$(GIT_VER)\"" -DPKG_VER="\"$(PKG_VER)\"" -DBUILD_DATE="\"$(BUILD_DATE)\"" -DINSTALL_PREFIX=\"$(INSTALL_PREFIX)\" $(LDFLAGS)
 
 ifeq ($(HAVE_XXD),y)
@@ -36,7 +36,6 @@ install: rpiboot
 	install -m 644 msd/bootcode.bin  $(INSTALL_PREFIX)/share/rpiboot/msd
 	install -m 644 msd/bootcode4.bin $(INSTALL_PREFIX)/share/rpiboot/msd
 	install -m 644 msd/start.elf  $(INSTALL_PREFIX)/share/rpiboot/msd
-	install -m 644 msd/start4.elf $(INSTALL_PREFIX)/share/rpiboot/msd
 	install -m 644 mass-storage-gadget64/boot.img $(INSTALL_PREFIX)/share/rpiboot/mass-storage-gadget64
 	install -m 644 mass-storage-gadget64/config.txt $(INSTALL_PREFIX)/share/rpiboot/mass-storage-gadget64
 	install -m 644 mass-storage-gadget64/bootfiles.bin $(INSTALL_PREFIX)/share/rpiboot/mass-storage-gadget64

main.c

@@ -10,7 +10,6 @@
 #include "msd/bootcode.h"
 #include "msd/start.h"
 #include "msd/bootcode4.h"
-#include "msd/start4.h"
 // 2712 doesn't use start5.elf
 
 /*
@@ -751,7 +750,7 @@ FILE * check_file(const char * dir, const char *fname, int use_fmem)
 			if(strcmp(fname, "bootcode4.bin") == 0)
 				fp = fmemopen(msd_bootcode4_bin, msd_bootcode4_bin_len, "rb");
 			else if(strcmp(fname, "start4.elf") == 0)
-				fp = fmemopen(msd_start4_elf, msd_start4_elf_len, "rb");
+				fp = fmemopen(msd_start_elf, msd_start_elf_len, "rb");
 		}
 		else
 		{