mfd: core: Make platform_data pointer const in struct mfd_cell

The content of the platform_data of a struct mfd_cell is simply passed on
to the platform_device_add_data() call in mfd_add_device() .

platform_device_add_data() already handles the data behind that pointer
as const and also uses kmemdup to create a copy of the data before
handing that copy over to the newly created platform-device,
so there is no reason to not extend this to struct mfd_cell, as the old
copy in the mfd_cell will be stale anyway.

This allows to pass structs gathered from of_device_get_match_data()
as platform-data to sub-devices - which is retrieved as const already.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20241107114712.538976-3-heiko@sntech.de


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