hw/pflash_cfi01: Make read after byte-write or erase return status

hw/pflash_cfi01: Make read after byte-write or erase return status

The Intel flash command set requires that a read operation after
doing a 'single byte write' command returns the status register;
add this case to pflash_read() so we return the correct information.
Similarly, the case for the 0x28 flavour of block erase was missing.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Tested-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 1358777318-7579-2-git-send-email-peter.maydell@linaro.org