Remove duplicate declaration of structure type
EFI_HII_POPUP_PROTOCOL from HiiPopup.h. The forward
declaration of the top of this file already declared
this type.
Cc: Liming Gao <gaoliming@byosoft.com.cn> Cc: Zhiguang Liu <zhiguang.liu@intel.com> Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com> Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>