Disable optimization for this function only with CPU_SAML1X MCUs due to an internal crosscompiler bug

Co-Authored-By: zhuoshuguo <zhuosgzju@gmail.com>

While trying python test libraries, like pytest, the automatic test collection
detects the `testNUM` functions as tests but does not know the `term` argument
and fails.

This declares them as private to only find `testfunc(child)` entry point.

Another solution could have been to use `testNUM(child)` and rename
`testfunc` to `main` but would not match other tests.

On samr30-xpro the tests takes respectively 20 and 14 seconds to complete

The default period value the application code is set to 2s

TESTS is used to find the tests files for the application but was used
to list test targets. Rename to COMPILE_TESTS as already done in some of
my other applications.

-) verify correctness of data written by raw write test
-) write to really last flash page and not last - 1
-) use flashpage_addr instead of manual calculation

Modify the test to accept slot values 0 and 1.

This way the IID generation gets much simplified and code duplication
is avoided since it removes GNRC's requirement for NETOPT_IPV6_IID.

drivers/tps6274x: initial support step-down converter
tests/driver_tps6274x: Added testcase for the step-down converter
boards/jiminy-mega256rfr2: Added TPS6274x config

Includes both server and client components.

The params argument is now a const pointer. This eliminates the need for
a type cast that converts a const to a non-const.

Since some boards an int is 16 bits the atoi truncates values.
This commit using a long instead of an int.

This states iotlab boards shouldn't run these tests.
This is because the i2c address of L3G4200 is the same ad the ds1307.
This causes an error that thinks the test is valid when it is not.

* drivers/ccs811: fix types in debug messages

* drivers/driver_ccs811_full: fix unused variable build error

Co-authored-by: Federico Pellegrin <fede@evolware.org>