overlays: ili9881-7inch: Fix overlay name in preamble

Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>

Author: nbuchwitz

arch/arm/boot/dts/overlays/vc4-kms-dsi-ili9881-7inch-overlay.dts

@@ -1,5 +1,5 @@
 /*
- * vc4-kms-dsi-ili9881-5inch-overlay.dts
+ * vc4-kms-dsi-ili9881-7inch-overlay.dts
  */
 
 /dts-v1/;