[SERIAL] kernel console should send CRLF not LFCR

Glen Turner reported that writing LFCR rather than the more
traditional CRLF causes issues with some terminals.

Since this aflicts many serial drivers, extract the common code
to a library function (uart_console_write) and arrange for each
driver to supply a "putchar" function.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>