linux-imx: Make the local version use -imx instead of -aiy

Change-Id: I2d58465ebdf954cf3af65503978a8ae6511b82a3
diff --git a/rootfs.mk b/rootfs.mk
index aecf0db..93b8299 100644
--- a/rootfs.mk
+++ b/rootfs.mk
@@ -22,7 +22,7 @@
 	imx-vpu-hantro \
 	imx-vpuwrap \
 	libdrm-vivante \
-	linux-image-4.9.51-aiy \
+	linux-image-4.9.51-imx \
 	python3-edgetpu \
 	python3-edgetpuvision \
 	uboot-imx \