mtd: st_spi_fsm: Search for preferred FSM message sequence configurations

Here we provide a means to traverse though all supplied FSM message
sequence configurations and pick one based on our chip's capabilities.
The first one we match will be the preferred one, as they are
presented in order of preference.

Acked-by Angus Clark <angus.clark@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>