hw/sd.c: Add missing state change for SD_STATUS, SEND_NUM_WR_BLOCKS

hw/sd.c: Add missing state change for SD_STATUS, SEND_NUM_WR_BLOCKS

The SD_STATUS and SEND_NUM_WR_BLOCKS commands are supposed to cause
the card to send data back to the host. However sd.c was missing the
state change to sd_sendingdata_state for these commands, with the effect
that the Linux driver would either hang indefinitely waiting for
nonexistent data (pl181) or read zeroes and provoke a qemu warning
message (omap).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>