MdeModulePkg/Ip4Dxe: Refine the coding style.

MdeModulePkg/Ip4Dxe: Refine the coding style.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1180
Remove the trailing white spaces.

Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Bi Dandan <dandan.bi@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Dandan Bi <dandan.bi@intel.com>