Fix error code on __zpl_ioctl_setflags()

Other (all?) Linux filesystems seem to return -EPERM instead of -EACCESS
when trying to set FS_APPEND_FL or FS_IMMUTABLE_FL without the
CAP_LINUX_IMMUTABLE capability. This was detected by generic/545 test
in the fstest suite.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Luis Henriques <henrix@camandro.org>
Closes #11791