ARM platforms: Fix console address for flush

The console core flush API expects the base address in the first
register, but ARM helpers currently sets the second register with the
base address. This causes an assert failure.

This patch fixes that.

Change-Id: Ic54c423cd60f2756902ab3cfc77b3de2ac45481e
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>