phy: Remove duplicated include in phy-fsl-lynx-28g.c

Fix following includecheck warning:
./drivers/phy/freescale/phy-fsl-lynx-28g.c: linux/workqueue.h is
included more than once.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220315235603.59481-1-yang.lee@linux.alibaba.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>