Per UEFI spec, on CallBack action EFI_BROWSER_ACTION_CHANGING, the return value of...

But, EDKII browser still processes the got ActionRequest. And, all HII drivers in EDKII project also returns their expected ActionRequest value on action EFI_BROWSER_ACTION_CHANGING.
Now update the browser to follow the spec, and update all core Hii drivers to keep old working modal.

Update for MdeModulePkg.

Signed-off-by: ydong10
Reviewed-by: lgao4
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12865 6f19259b-4bc3-4df7-8a09-765794883524