tests: gpio-mockup: don't allocate the chip structure twice
tests: gpio-mockup: don't allocate the chip structure twice

We incorrectly allocate the chip structure twice: once in
gpio_mockup_probe() and then again in make_chip() which leads to a
memory leak. Remove the first instance as it's the one that's
unnecessary.

Fixes: e43e46d4f79c ("tests: mockup: add a library for controlling the gpio-mockup module")
Signed-off-by: Bartosz Golaszewski <e5d45fddd9040473413b909b802f629a971ad04c@baylibre.com>

brgl/libgpiod,brgl/libgpiod,brgl/libgpiod,brgl/libgpiod