drivers: net: xilinx_emaclite: Add COMPILE_TEST support

commit 03dfd157

 upstream.

To improve build testing of this driver, add COMPILE_TEST support.

Acked-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>