serial: sirf: fix the namespace of startup_uart entry

startup_uart_controller() loses namespace, this patch
drops the function directly and move the content into
sirfsoc_uart_startup().

Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>