iwlwifi: de-const properly where needed

In order to de-const variables simply casting through (void *) is
not enough: "cast from 'const .. *' to 'void *' drops const qualifier".
Cast through (uintptr_t) as well [1] to make this compile on systems
with more strict requirements.
In addition passing const void *data to dma_map_single() also
drops the (const) qualifier.  De-constify on variable on assignment
which may be overwritten later.  In either case the (void *) cast
to dma_map_single() is not needed (anymore) either.

[1] See __DECONST() in sys/sys/cdefs.h in FreeBSD

Sponsored by:  The FreeBSD Foundation
Signed-off-by: Bjoern A. Zeeb <bz@FreeBSD.ORG>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20220128153014.eb696eb56bf6.Ide1dd041f9b908c5154a600286a7453750b0704a@changeid


Signed-off-by: Luca Coelho <luciano.coelho@intel.com>