LinuxKPI: devres: divorce dem_kfree from lkpi_devm_kmalloc_release

dem_kfree() is called from all over the place and should actually
do something; contrary to lkpi_devm_kmalloc_release() it can also
take a const void *. We have to __DECONST() that though as the
entire devres framework does otherwise not take a const argument.

This was discovered during the rtw89 upadte to 6.16.

Sponsored by: The FreeBSD Foundation (initially)
MFC after: 3 days
Reviewed by: dumbbell
Differential Revision: https://reviews.freebsd.org/D52082