lib/test_linear_ranges: Use LINEAR_RANGE()

New initialization macro for linear ranges was added. Slightly simplify
the test code by using this macro - and at the same time also verify the
macro is working as intended.

Use the newly added LINEAR_RANGE() initialization macro for linear range
test.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://lore.kernel.org/r/Y3R13IRrs+x5PcZ4@dc75zzyyyyyyyyyyyyydt-3.rev.dnainternet.fi


Signed-off-by: Mark Brown <broonie@kernel.org>