build: increment the revision in libgpiomockup's ABI version
build: increment the revision in libgpiomockup's ABI version

This helper library too has a separate ABI version, but we missed it
when incrementing other ABI numbers for v1.5-rc1. Increment the revision
only as no new interfaces were added or old ones removed.

Signed-off-by: Bartosz Golaszewski <e5d45fddd9040473413b909b802f629a971ad04c@baylibre.com>

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