mfd: db8500: Update BML clock register for db8580

BML clock register address in DB8580 has changed.Defined a new address
under different name for DB8580.

Signed-off-by: Philippe Begnic <philippe.begnic@st.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>