hw/sd.c: Correct handling of type B SD status bits

Correct how we handle the type B ("cleared on valid command")
status bits. In particular, the CURRENT_STATE bits in a response
should be the state of the card when it received that command,
not the state when it received the preceding command. (This is
one of the issues noted in LP:597641.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Andrzej Zaborowski <andrew.zaborowski@intel.com>
