feat(sgi): route TF-A logs via secure uart

Route the boot, runtime and crash stage logs via secure UART port
instead of the existing use of non-secure UART. This aligns with the
security state the PE is in when logs are put out. In addition to this,
this allows consolidation of the UART related macros across all the
variants of the Neoverse reference design platforms.

Signed-off-by: Rohit Mathew <rohit.mathew@arm.com>
Change-Id: I417f5d16457b602c94da4c74b4d88bba03da7462