configs/mx53loco: Adjust comment to reflect the real kernel version

The kernel used is from 4.16 version, so adjust the comment.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

configs/mx53loco_defconfig

@@ -2,7 +2,7 @@
 BR2_arm=y
 BR2_cortex_a8=y
 
-# Linux headers same as kernel, a 4.15 series
+# Linux headers same as kernel, a 4.16 series
 BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_16=y
 
 # System