zram: switch to guard() for init_lock

zram: switch to guard() for init_lock

Use init_lock guard() in sysfs store/show handlers, in order to simplify
and, more importantly, to modernize the code.

While at it, fix up more coding styles.

Link: https://lkml.kernel.org/r/20251201094754.4149975-7-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Stevens <stevensd@google.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Richard Chang <richardycc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>