staging: silicom: remove dead code

bus_info field of struct ethtool_drvinfo is an array thus it always
evaluates to true in a boolean context.  Therefore operation
depending on it being false will never be executed.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>