hw/dma: sifive_pdma: permit 4/8-byte access size of PDMA registers

hw/dma: sifive_pdma: permit 4/8-byte access size of PDMA registers

It's obvious that PDMA supports 64-bit access of 64-bit registers, and
in previous commit, we confirm that PDMA supports 32-bit access of
both 32/64-bit registers. Thus, we configure 32/64-bit memory access
of PDMA registers as valid in general.

Signed-off-by: Jim Shu <jim.shu@sifive.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Message-id: 20220104063408.658169-3-jim.shu@sifive.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>