mtd: nand: fsmc: remove stale non-DT probe path

The FSMC driver has an execution path and a header file in
<linux/mtd/fsmc.h> that serves to support passing in platform
data through board files, albeit no upstream users of this
mechanism exist.

The header file also contains function headers for functions that
do not exist in the kernel.

Delete this and move the platform data struct, parsing and
handling into the driver, assume we are using OF and make the
driver depend on OF, remove the ifdefs making that optional.

Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Stefan Roese <sr@denx.de>
Cc: Vipin Kumar <vipin.kumar@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>