Linux 6.8 compat: fix inode permission tests

The name inode_permission is now defined in the kernel. Rename ours to
test_permission, in line with most of our other tests.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Sponsored-by: https://despairlabs.com/sponsor/
Closes #15805