msm: 8x25: board: share the same ADM channel between NAND and eMMC

Currently for MSM8x25, all the SDCC slots share
the same ADM channel. This means both SD and eMMC card slots
will share the same ADM channel. But as SD card can be hot pluggable,
SD card insertion/removal can cause the ADM channel flush which
possibly can affect the ongoing transfer on eMMC (as it shares the
same ADM channel with SD card).

On the other hand, we generally have either eMMC or NAND flash device
active on any platform. So if eMMC is used, NAND won't be used or
mostly not present on board. This means eMMC slot can use the same
ADM channel which NAND uses and this way both SD and eMMC slots will
have separate ADM channel.

Change-Id: Ib0ff3bc87a46e5101ad3203b4ea097f3567a1d3a
Signed-off-by: Pratibhasagar V <pratibha@codeaurora.org>