EmulatorPkg/(Pei|Dxe)EmuSerialPortLib: Remove the SerialPortExtLib functions from...

EmulatorPkg/(Pei|Dxe)EmuSerialPortLib: Remove the SerialPortExtLib functions from SerialPortLib

SerialPortSetControl, SerialPortGetControl and SerialPortSetAttributes are functions
of the SerialPortExtLib library interface. They should not be implemented by the
SerialPortLib library.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <Olivier.martin@arm.com>
Reviewed-by: Andrew Fish <afish@apple.com>
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14357 6f19259b-4bc3-4df7-8a09-765794883524