bindings: python: directly return the value from PyErr_SetFromErrno()
bindings: python: directly return the value from PyErr_SetFromErrno()

PyErr_SetFromErrno() always returns NULL. We can return from functions
on failure directly instead of calling it and then returning NULL in
the next line.

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

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