net: fec: Silence M5272 build warnings

If CONFIG_M5272=y:

    drivers/net/ethernet/freescale/fec_main.c: In function ‘fec_restart’:
    drivers/net/ethernet/freescale/fec_main.c:948:6: warning: unused variable ‘val’ [-Wunused-variable]
      948 |  u32 val;
	  |      ^~~
    drivers/net/ethernet/freescale/fec_main.c: In function ‘fec_get_mac’:
    drivers/net/ethernet/freescale/fec_main.c:1667:28: warning: unused variable ‘pdata’ [-Wunused-variable]
     1667 |  struct fec_platform_data *pdata = dev_get_platdata(&fep->pdev->dev);
	  |                            ^~~~~

Fix this by moving the variable declarations inside the existing #ifdef
blocks.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210202130650.865023-1-geert@linux-m68k.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>