of: unittest: Fix overlay type in apply/revert check

The removal check in of_unittest_apply_revert_overlay_check()
always uses the platform device overlay type, while it should use the
actual overlay type, as passed as a parameter to the function.

This has no impact on any current test, as all tests calling
of_unittest_apply_revert_overlay_check() use the platform device overlay
type.

Fixes: d5e75500 ("of: unitest: Add I2C overlay unit tests.")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/ba0234c41ba808f10112094f88792beeb6dbaedf.1690533838.git.geert+renesas@glider.be


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