Restore FreeBSD to use .rodata
In https://github.com/openzfs/zfs/pull/14228 the FreeBSD
SECTION_STATIC was set to ".data" instead of ".rodata". This
commit just restores it back to .rodata.
Reviewed-by: Attila Fülöp <attila@fueloep.org>
Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Jorgen Lundman <lundman@lundman.net>
Closes #14460