powerpc/64s/radix: Remove need_flush_all test from radix__tlb_flush

need_flush_all is only set by arch code to instruct generic tlb_flush
to flush all. It is never set by powerpc, so it can be removed.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230203111718.1149852-2-npiggin@gmail.com