mtd: st_spi_fsm: Supply the N25Qxxx specific read configurations

The N25Qxxx Serial Flash devices required different sequence
configurations depending on whether they're running in 24bit (3Byte)
or 32bit (4Byte) mode. We provide those here.

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>