mmc: card: activate packing control only for eMMC4.5 cards

Since the write packing is an eMMc4.5 feature, packing control
should also be activated only for eMMc4.5 cards.

Change-Id: If094658943a536f39afc814f6684c0dbb0806778
Signed-off-by: Maya Erez <merez@codeaurora.org>