skd: Remove superfluous occurrences of the 'volatile' keyword

skd: Remove superfluous occurrences of the 'volatile' keyword

mem_map[i] is accessed through readl() / writel() hence declaring
mem_map as volatile is not necessary.

Remove the volatile declarations from struct fit_completion_entry_v1
pointers and struct fit_comp_error_info since reading these structures
multiple times is safe.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>