mmc: support packed write command for eMMC4.5 device

This patch supports packed write command of eMMC4.5 device.
Several writes can be grouped in packed command and all data
of the individual commands can be sent in a single transfer
on the bus.

Change-Id: I7d3695c7241b2df7c504673bb91366eabba648ff
Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
Reviewed-by: Maya Erez <merez@codeaurora.org>
Reviewed-by: Namjae Jeon <linkinjeon@gmail.com>

[tlinder@codeaurora.org: Difference in definition:
R1_EXP_EVENT -- > R1_EXCEPTION_EVENT]

Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>