hw/block: m25p80: Support fast read for SST flashes

Per SST25VF016B datasheet [1], SST flash requires a dummy byte after
the address bytes. Note only SPI mode is supported by SST flashes.

[1] http://ww1.microchip.com/downloads/en/devicedoc/s71271_04.pdf



Signed-off-by: Bin Meng <bin.meng@windriver.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210306060152.7250-1-bmeng.cn@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>