zram: move immutable comp params away from per-CPU context

zram: move immutable comp params away from per-CPU context

Immutable params never change once comp has been allocated
and setup, so we don't need to store multiple copies of
them in each per-CPU backend context.  Move those to
per-comp zcomp_params and pass it to backends callbacks
for requests execution.  Basically, this means parameters
sharing between different contexts.

Also introduce two new backends callbacks: setup_params()
and release_params().  First, we need to validate params
in a driver-specific way; second, driver may want to
allocate its specific representation of the params which
is needed to execute requests.

Link: https://lkml.kernel.org/r/20240712051850.484318-20-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nick Terrell <terrelln@fb.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>