mfd: core: Increment of_node's refcount before linking it to the platform device

When an MFD device is added, a platform_device is allocated. If this
device is linked to a DT description, the corresponding OF node is linked
to the new platform device but the OF node's refcount isn't incremented.
As of_node_put() is called during the platform device release, it leads
to a refcount underflow.

Call of_node_get() to increment the OF node's refcount when the node is
linked to the newly created platform device.

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
Link: https://lore.kernel.org/r/20250820-mfd-refcount-v1-1-6dcb5eb41756@bootlin.com


Signed-off-by: Lee Jones <lee@kernel.org>