Review shell scripts

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/eirene/hardware/scripts/card.sh

@@ -1,10 +1,10 @@
 AMD=/dev/dri/by-path/pci-0000:06:00.0-card
 NVIDIA=/dev/dri/by-path/pci-0000:01:00.0-card
 
-if [[ -e "${AMD}" ]]; then
-  CARD=${AMD}
+if [[ -e "$AMD" ]]; then
+  card=$AMD
 else
-  CARD=${NVIDIA}
+  card=$NVIDIA
 fi
 
-ln -sf "${CARD}" "${HOME}"/.config/hypr/card
+ln -sf "$card" "$HOME"/.config/hypr/card