Previously Soft Reset (clear of SRST bit in UCR2 register)
of UART in startup is not protected by lock, which may have race
with console_write, as console_write may occur at anytime even
when UART port is shutdown.

To avoid this race, protect Soft reset of UART port with spin_lock.
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>