mtd: st_spi_fsm: Supply the S25FLxxx chip specific configuration call-back

This patch allows us to prepare some of the message sequences which will
be required to talk to the  S25FLxxx family of Serial Flash devices. It
also allows us to do some required extra operations after any busy wait
failures.

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>