MdePkg/HiiImageEx: Fix incorrect parameter type in GetImageInfo()

MdePkg/HiiImageEx: Fix incorrect parameter type in GetImageInfo()

In latest UEFI2.6 spec, the type of the fourth parameter in function
GetImageInfo() is "EFI_IMAGE_OUTPUT", but in the header file, it is
"EFI_IMAGE_INPUT". Now correct it to follow the spec.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Cecil Sheng <cecil.sheng@hpe.com>
Cc: Abner Chang <abner.chang@hpe.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>