of: unittest: Add a test case for of_changeset_add_prop_bool()

Improve of_unittest_changeset_prop() to have a test case for the
newly introduced of_changeset_add_prop_bool().

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Link: https://lore.kernel.org/r/20240527161450.326615-17-herve.codina@bootlin.com


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>