x86: bump default kernel partition size to 16M

This leaves more room for sysupgrade config data or for having multiple
kernel images to choose from

Signed-off-by: Felix Fietkau <[email protected]>

config/Config-images.in

@@ -248,7 +248,7 @@ menu "Target Images"
 	config TARGET_KERNEL_PARTSIZE
 		int "Kernel partition size (in MB)"
 		depends on GRUB_IMAGES
-		default 4
+		default 16
 
 	config TARGET_ROOTFS_PARTSIZE
 		int "Root filesystem partition size (in MB)"