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: NAbaci Robot <abaci@linux.alibaba.com>
Signed-off-by: NYang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220315235603.59481-1-yang.lee@linux.alibaba.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

drivers/phy/freescale/phy-fsl-lynx-28g.c

@@ -6,7 +6,6 @@
 #include <linux/phy/phy.h>
 #include <linux/platform_device.h>
 #include <linux/workqueue.h>
-#include <linux/workqueue.h>
 
 #define LYNX_28G_NUM_LANE			8
 #define LYNX_28G_NUM_PLL			2