StdLib: Fix compilation errors caused by previous commit of daConsole.c

StdLib: Fix compilation errors caused by previous commit of daConsole.c

Move functions da_ConFlush and da_ConClose to just before da_ConPoll so that
they are defined after any calls to them.

Replace da_ConFlush with the actual final implementation instead of the
initial version which was committed.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Daryl McDaniel <edk2-lists@mc2research.org>
Reviewed-by: Michael Zimmermann <sigmaepsilon92@gmail.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19627 6f19259b-4bc3-4df7-8a09-765794883524