net: phy: bcm-phy-lib: Fix module license issue

The 'bcm-phy-lib.c', added as a part of the commit
"net: phy: Add Broadcom phy library for common interfaces"
was missing the module license. This was causing an issue
when the library is built as a module; "module license
'unspecified' taints kernel".

This patch fixes the issue by adding the module license,
author and description to the bcm-phy-lib.c file.

Fixes: a1cba561 ("net: phy: Add Broadcom phy library for
common interfaces")
Signed-off-by: Arun Parameswaran <arunp@broadcom.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>