MdeModulePkg/ScsiDisk: Return EFI_NO_MEDIA when no media presents

Current code always return EFI_MEDIA_CHANGED no matter the media
is removed from CD/DVD drive or the media is changed.
It doesn't strictly follow the UEFI Spec.
Update code to return EFI_NO_MEDIA when media is removed.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>