MdeModulePkg FormBrowserEx: Change its structure name with EDKII_ prefix

MdeModulePkg FormBrowserEx: Change its structure name with EDKII_ prefix

EDKII implementation protocol should be with EDKII_ prefix.

V2: add gEdkiiFormBrowserExProtocolGuid to align its structure name.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>