lib/genalloc: fix device leak in of_gen_pool_get()

lib/genalloc: fix device leak in of_gen_pool_get()

Make sure to drop the reference taken when looking up the genpool platform
device in of_gen_pool_get() before returning the pool.

Note that holding a reference to a device does typically not prevent its
devres managed resources from being released so there is no point in
keeping the reference.

Link: https://lkml.kernel.org/r/20250924080207.18006-1-johan@kernel.org
Fixes: 9375db07adea ("genalloc: add devres support, allow to find a managed pool by device")
Signed-off-by: Johan Hovold <johan@kernel.org>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Vladimir Zapolskiy <vz@mleia.com>
Cc: <stable@vger.kernel.org>	[3.10+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>