raspberryPi boot loader: don't remove xx-initrd files

The Raspberry Pi boot loader was deleting all xx-initrd text files
(which simply contain the path to the actual initrd files) just after
having created them. The code was actually trying to delete real,
obsolete initrd files, which are named <hash>-initrd-initrd (after path
cleaning), but the glob was catching the other files as well.

nixos/modules/system/boot/loader/raspberrypi/builder.sh

@@ -115,7 +115,7 @@ copyForced $fwdir/start_db.elf  /boot/start_db.elf
 copyForced $fwdir/start_x.elf   /boot/start_x.elf
 
 # Remove obsolete files from /boot and /boot/old.
-for fn in /boot/old/*linux* /boot/old/*initrd* /boot/bcm*.dtb; do
+for fn in /boot/old/*linux* /boot/old/*initrd-initrd* /boot/bcm*.dtb; do
     if ! test "${filesCopied[$fn]}" = 1; then
         rm -vf -- "$fn"
     fi