OvmfPkg: describe debug messages in the README file

Contributed-under: TianoCore Contribution Agreement 1.0

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14364 6f19259b-4bc3-4df7-8a09-765794883524
EmbeddedPkg/SerialPortExtLib.h: Changed SerialPortSetAttributes() prototype to return the set value(s)

To be compliant with the UEFI specification it is required to update SERIAL_IO_MODE with the values set.
This prototype change allows to get the value used inside SerialPortSetAttributes().

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <Olivier.martin@arm.com>



git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14365 6f19259b-4bc3-4df7-8a09-765794883524