gpiolib: handle gpio-hogs only once

gpiolib: handle gpio-hogs only once

Commit d1d564ec49929 ("gpio: move hogs into GPIO core") introduced a
behaviour change that breaks boot on Raspberry Pi 5 when using the
firmware-supplied device tree:

  gpiochip_add_data_with_key: GPIOs 544..575
    (/soc@107c000000/gpio@7d517c00) failed to register, -22
  brcmstb-gpio 107d517c00.gpio: Could not add gpiochip for bank 1
  brcmstb-gpio 107d517c00.gpio: probe with driver brcmstb-gpio failed
    with error -22

gpio-brcmstb registers two gpio_chips against the device tree
node gpio@7d517c00, one for each bank. The firmware-supplied DT includes
a gpio-hog on RP1 RUN, and this gpio-hog is attempted to be applied to
*both* gpio_chips. This succeeds against bank 0 (which hosts the GPIO)
and fails for bank 1 (which does not).

In the previous implementation, failures to apply gpio-hogs were
quietly ignored. In the new code, the error code propagates and causes
probe to fail.

Closely approximate the previous behaviour by using the OF_POPULATED flag
to ensure that each gpio-hog is processed only once. The flag was
previously being set before the gpio-hogs were processed, so as part
of this change, the flag now gets set only after the gpio-hog is actioned.
The handling of gpio-hogs on a DT node with multiple gpio_chips remains a
bit incomplete/unclear, but this at least retains the ability to apply
hogs to the first gpio_chip per node.

Fixes: d1d564ec49929 ("gpio: move hogs into GPIO core")
Signed-off-by: Daniel Drake <dan@reactivated.net>
Link: https://patch.msgid.link/20260608210108.36248-1-dan@reactivated.net
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>