As per the SD physical layer specification version 7.10, erase
command (CMD38) and stop transmission command (CMD12) will generate
R1b response.

R1b = R1 + busy signal

A non-zero value after the R1 response indicates card is ready for
next command.

Signed-off-by: Pragnesh Patel <[email protected]>
Reviewed-by: Bin Meng <[email protected]>
Tested-by: Bin Meng <[email protected]>