Similar to the device parameter functions also make the globalvar
functions more consistent. This also adds support for readonly
globalvars and changes several existing globalvars which should
really be readonly to readonly.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

We have our file helper functions in several places. Move them
all to lib/libfile.c.
With this we no longer have file helpers in fs/fs.c which contains
the core fs functions and no functions in lib/libbb.c which are
not from busybox.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Calling globalvar_add_simple() and setting a value is more than common.
Add a parameter for the initial value.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

As new breakout boards are being developped, we need to add their IDs in
the device detection code, otherwise they will be treated as regular
CFA-10036.

Signed-off-by: Brian Lilly <brian@crystalfontz.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

The AT24 found on the expansion boards store the variant of the board it
is soldered onto.

That means that we are that way able to determine what expansion board
is currently plugged in if any. If we can't communicate with the EEPROM,
we just assume that only the CFA-10036 is there.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>