ACPI: APEI: EINJ: Fix resource leak by remove callback in .exit.text

ACPI: APEI: EINJ: Fix resource leak by remove callback in .exit.text

The .remove() callback is also used during error handling in
faux_probe(). As einj_remove() was marked with __exit it's not linked
into the kernel if the driver is built-in, potentially resulting in
resource leaks.

Also remove the comment justifying the __exit annotation which doesn't
apply any more since the driver was converted to the faux device
interface.

Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Cc: 6.16+ <stable@vger.kernel.org> # 6.16+
Link: https://patch.msgid.link/20250814051157.35867-2-u.kleine-koenig@baylibre.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>