ci/bare-metal: Increase maximum retry count for POE boots.

The manual jetson CI job I'm introducing has serious boot reliability
trouble, but also we've seen frequent intermittent failures on bcm where
at least 2 boots don't seem to be enough (#6041).

Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15201>

.gitlab-ci/bare-metal/poe-powered.sh

@@ -111,7 +111,7 @@ echo "$BM_CMDLINE" > /tftp/cmdline.txt
 printf "$BM_BOOTCONFIG" >> /tftp/config.txt
 
 set +e
-ATTEMPTS=2
+ATTEMPTS=10
 while [ $((ATTEMPTS--)) -gt 0 ]; do
   python3 $BM/poe_run.py \
           --dev="$BM_SERIAL" \