staging: vchiq: fix __user annotations

staging: vchiq: fix __user annotations

My earlier patches caused some new sparse warnings, but it turns out
that a number of those are actual bugs, or at least suspicous code.

Adding __user annotations to the data structures that are defined in
uapi headers helps avoid the new warnings, but that causes a different
set of warnings to show up, as some of these structures are used both
inside of the kernel and at the user interface but storing pointers to
different things there.

Duplicating the vchiq_service_params and vchiq_completion_data structures
in turn takes care of most of those, and then it turns out that there
is a 'data' pointer that can be any of a __user address, a dmd_addr_t
and a kernel pointer in vmalloc space at times.

I'm trying to annotate these as best I can without changing behavior,
but there still seems to be a serious bug when user space passes
a valid vmalloc space address instead of a user pointer. Adding
comments in the code there, and leaving the warnings in place that
seem to correspond to actual bugs.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200925114424.2647144-1-arnd@arndb.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>