This function ensures that console output is flushed, for example
before shutting down or use by another component

In line with other console APIs, console_flush() wraps
console_core_flush().

Also implement console_core_flush() for PL011.

Change-Id: I3db365065e4de04a454a5c2ce21be335a23a01e4
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This patch adds console drivers including the pl011 driver
for the AArch32 mode.

Change-Id: Ifd22520d370fca3e73dbbf6f2d97d6aee65b67dd