doc/icE1usb: Add link to older firmware builds

Change-Id: I8b97efbe4a644e5b9bbdec0bc764d55f7b59d2d2
---
M doc/manuals/chapters/firmware.adoc
1 file changed, 2 insertions(+), 0 deletions(-)

diff --git a/doc/manuals/chapters/firmware.adoc b/doc/manuals/chapters/firmware.adoc
index 069a2ba..3b47206 100644
--- a/doc/manuals/chapters/firmware.adoc
+++ b/doc/manuals/chapters/firmware.adoc
@@ -47,6 +47,8 @@
 
 The latest firmware can be found at
 https://ftp.osmocom.org/binaries/icE1usb/firmware/latest/
+a backlog of earlier builds can be found at
+https://ftp.osmocom.org/binaries/icE1usb/firmware/all/
 
 The latest gateware can currently only be found at the personal developer
 directory of tnt at https://people.osmocom.org/tnt/ice1usb/icE1usb-202010-bd399e96.bin

