imx: kontron-sl-mx8mm: Prepare for I2C display detection in environment script

Enable the I2C bus and set a env variable for the reset GPIO of the touch
controller. This allows us to probe the panel in a script.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Fabio Estevam <festevam@denx.de>
diff --git a/board/kontron/sl-mx8mm/sl-mx8mm.c b/board/kontron/sl-mx8mm/sl-mx8mm.c
index 6411301..4ac430b 100644
--- a/board/kontron/sl-mx8mm/sl-mx8mm.c
+++ b/board/kontron/sl-mx8mm/sl-mx8mm.c
@@ -126,8 +126,11 @@
 	if (!fdt_node_check_compatible(gd->fdt_blob, 0, "kontron,imx8mm-n802x-som") ||
 	    !fdt_node_check_compatible(gd->fdt_blob, 0, "kontron,imx8mm-osm-s")) {
 		env_set("som_type", "osm-s");
-	else
+		env_set("touch_rst_gpio", "111");
+	} else {
 		env_set("som_type", "sl");
+		env_set("touch_rst_gpio", "87");
+	}
 
 	return 0;
 }