ShellPkg: decode serial console attribute set failure status when used thru sermode...

ShellPkg: decode serial console attribute set failure status when used thru sermode command

Serial console driver may not support all databits / stopbits attribute values.
But ‘sermode’ command only displays a general error indicating operation failure.
Instead it should decode error status and report more accurate error message.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Tapan Shah <tapandshah@hp.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17978 6f19259b-4bc3-4df7-8a09-765794883524