linux/linux-ext-*.mk: fit file header into one line
Make it follow the package coding style by removing redundant info.
Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Cc: Christian Stewart <christian@paral.in>
Cc: David Lechner <david@lechnology.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>