spl-generic.c defines some of the libgcc integer library functions on
32-bit. Don't bother checking -Wmissing-prototypes since nothing should
directly call these functions from C code.
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Closes#10470