Update tmpfile() existence detection

Linux changed the tmpfile() signature again in torvalds/linux@6521f89,
which in turn broke our HAVE_TMPFILE detection in configure.

Update that macro to include the new case, and change the signature of
zpl_tmpfile as appropriate.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes: #12060
Closes: #12087