mmc: mmc_spi: Generate R1 response for erase block start and end address

Erase block start address (CMD32) and erase block end address (CMD33)
command will generate R1 response for mmc SPI mode.

R1 response is 1 byte long for mmc SPI, so assign 1 byte as a response
for this commands.

Signed-off-by: Pragnesh Patel <pragnesh.patel@sifive.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Tested-by: Bin Meng <bin.meng@windriver.com>