Fix clang 13 compilation errors
os/linux/zfs/zvol_os.c:1111:3: error: ignoring return value of function
declared with 'warn_unused_result' attribute [-Werror,-Wunused-result]
add_disk(zv->zv_zso->zvo_disk);
^~~~~~~~ ~~~~~~~~~~~~~~~~~~~~
zpl_xattr.c:1579:1: warning: no previous prototype for function
'zpl_posix_acl_release_impl' [-Wmissing-prototypes]Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: szubersk <szuberskidamian@gmail.com>
Closes #13551
(cherry picked from commit 988431966639d791ac269011d136e85f3602df75)