hw/dma: sifive_pdma: Fix Control.claim bit detection

At present the codes detect whether the DMA channel is claimed by:

  claimed = !!s->chan[ch].control & CONTROL_CLAIM;

As ! has higher precedence over & (bitwise and), this is essentially

  claimed = (!!s->chan[ch].control) & CONTROL_CLAIM;

which is wrong, as any non-zero bit set in the control register will
produce a result of a claimed channel.

Fixes: de7c7988 ("hw/dma: sifive_pdma: reset Next* registers when Control.claim is set")
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20210927072124.1564129-1-bmeng.cn@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>