Previous commit 354e27dd introduced a dependency upon IIO_GASRESISTANCE
being defined as a member of enum iio_chan_type.  The enum is part of
the kernel headers and not part of the out-of-tree IIO code in the
mangOH repository.  The code now checks that
CONFIG_IIO_CHAN_TYPE_GASRESISTANCE is defined before trying to reference
IIO_GASRESISTANCE.

By using the componentSearch feature, more of the build requirements can
be specified in the SDEF instead of the Makefile.  componentSearch is a
Legato 18.04.0 feature.

The mangOH build is failing in the developer VM based on Ubuntu 18.04
because the wrong toolchain is being selected for the red_wp85 build.  I
think the root cause may have to do with the .phony target that sets up
the Make variables not being run multiple times.  Rather than spending a
lot of time on this, I have just simplified the Makefile so that the
problem goes away.

Points to last master commit for RedSensorToCloud

The removal of the i2c-utils package from WP76/WP77 release 8 broke the
GpioExpanderService.  This commit includes an update to
GpioExpanderService which adds a header that implements the removed
functionality.

The variable MANGOH_I2C_BUS_BATTERY has been introduced in the targets
files for 9x15 and 9x07 because the I2C bus numbering differs.  The
batteryService app has been updated to use this variable.

In this version the app model and adef have matching version numbers
(2.0)

The battery gauge was disabled on wp76/77 because of a lockup in the
power supply kernel subsystem when the battery gauge driver was
unloaded.  This has been fixed in release 8 and thus the battery gauge
driver and battery service can be enabled.  The battery gauge and
battery service still aren't usable on wp75/85 because of a different
kernel bug.

Added script used to configure the MangOH to route to/from
local LAN interface, i.e. eth0 to/from the cellular WAN interface,
i.e. rmnet-data0.

The mangOH makefile now reads a $LEGATO variable to decide if the Legato
framework at $LEGATO_ROOT should be built.  Previously, but variable
$NO_BUILD_LEGATO was used, but this was a bit verbose.

Also support building of multiple targets with correct toolchains with
one invocation of make.