lib: Fix multiple definitions of clz_tab

Both sparc 32-bit's software divide assembler and MPILIB provide
clz_tab[] with identical contents.

Break it out into a seperate object file and select it when
SPARC32 or MPILIB is set.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: James Morris <jmorris@namei.org>