test_rhashtable: remove initdata annotation

kbuild test robot reported a section mismatch warning w. gcc 4.x:
WARNING: lib/test_rhashtable.o(.text+0x139e):
Section mismatch in reference from the function rhltable_insert.clone.3() to the variable .init.data:rhlt

so remove this annotation.

Fixes: cdd4de37 ("test_rhashtable: add test case for rhl_table interface")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>