MdeModulePkg ScsiDiskDxe: Fix hang issue when reconnecting an ISCSI device

MdeModulePkg ScsiDiskDxe: Fix hang issue when reconnecting an ISCSI device

The 'Reset' function for BlockIO(2) in ScsiDiskDxe should return
EFI_SUCCESS instead of EFI_DEVICE_ERROR when a device does not support
reset feature.

Otherwise, a 'reconnect -r' action when an ISCSI device is attached will
cause system hang.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>