mmc: CMD7:MMC_CMD_SELECT_CARD response fix

As per JEDEC document JESD84-A441 (page 105) response for CMD7
(MMC_CMD_SELECT_CARD) response should be R1 instead of R1b. In uboot we
never take MMC to disconnected state and on powerup its always ideal
state which later goes to stand-by state.

from document footnote:
R1 while selecting from Stand-By State to Transfer State; R1b while
selecting from Disconnected State to Programming State.

Signed-off-by: Ajay Bhargav <ajay.bhargav@einfochips.com>