uniphier: support console based on multi-console

uniphier: support console based on  multi-console

The legacy console is gone. Re-add the console support based on the
multi-console framework.

I am still keeping the putc, getc, and flush callbacks in
uniphier_console.S to use plat/common/aarch64/crash_console_helpers.S

The console registration code already relies on that C environment
has been set up. So, I just filled the struct console fields with the
callback pointers, then called console_register() directly. I also
re-implemented the init function in C to improve the readability.

Removing the custom crash console implementation has one disadvantage;
we cannot use the crash console on very early crashes because
crash_console_helpers.S works only after the console is registered.
I can live with this limitation.

Tested on my boards, and confirmed this worked like before.

Change-Id: Ieab9c849853ff6c525c15ea894a85944f257db59
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>