net/phy/bcm87xx: Add MODULE_LICENSE("GPL") to GPL driver

Currently the driver has no MODULE_LICENSE attribute in its source which
results in a kernel taint if I load this:

root@(none):~# modprobe bcm87xx
bcm87xx: module license 'unspecified' taints kernel.

Since the first lines of the source code clearly state:
* This file is subject to the terms and conditions of the GNU General
* Public License. See the file "COPYING" in the main directory of this
* archive for more details.
I think it's safe to add the MODULE_LICENSE("GPL") macro and thus remove
the kernel taint.

Cc: [e-mail]
Signed-off-by: Peter Huewe <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/bcm87xx.c

···
 		ARRAY_SIZE(bcm87xx_driver));
 }
 module_exit(bcm87xx_exit);
+
+MODULE_LICENSE("GPL");