ShellPkg/[hex]edit: Fix CTRL+<Alpha> doesn't work from hyper terminal

After commit 20ddbc133f679b7895dfdaf2fd58ec4c8183a1d8
* MdeModulePkg/ConSplitter: ReadKeyStrokeEx always return key state

When one physical console supports to report the shift key state,
the key data returned from ConSplitter driver at least carries
the shift key valid bit.
The patch fixes the edit/hexedit to accept Unicode (1) when
the no shift key is pressed or reported.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>