Ensure a console is initialized before it is used

This patch moves console_init() to bl32_early_platform_setup(). It
also ensures that console_init() is called in each
blX_early_platform_setup() function before the console is used
e.g. through a printf call in an assert() statement.

Fixes ARM-software/TF-issues#127

Change-Id: I5b1f17e0152bab674d807d2a95ff3689c5d4794e