staging: vchiq_arm: cast with __force as needed

In several cases where a pointer marked as __user is
(intentionally) assigned or passed to a non-marked target,
cast to the target pointer type with a __force directive
to quiet warnings from sparse.

Signed-off-by: Mitchell Tasman <tasman@leaflabs.com>
Link: https://lore.kernel.org/r/20200519004531.33158-1-tasman@leaflabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>