serial: st-asc: Change default baudrate from 9600 to 115200

9600 is old school.

Most applications use 115200 as the default baud these days.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>