fix: greeter compositor — replace bash process substitution with POSIX for loop

redbear-greeter-compositor: line 35 was using 'done < <(cmd)'
bash process substitution which creates /dev/fd/63. Redox kernel
does not implement /dev/fd, causing 'No such file or directory'
error and compositor startup failure.

Replaced 'while read; do ...; done < <(parse_drm_devices)' with
'for device in ; do ...; done' — pure POSIX,
no /dev/fd dependency. Device names contain no whitespace so
word splitting is correct for this use case.

local/recipes/system/redbear-greeter/source/redbear-greeter-compositor

@@ -36,11 +36,11 @@ drm_devices_ready() {
     local devices="${1:-}"
     local device=""
 
-    while IFS= read -r device; do
+    for device in $(parse_drm_devices "$devices"); do
         if [ ! -e "$device" ]; then
             return 1
         fi
-    done < <(parse_drm_devices "$devices")
+    done
 
     return 0
 }