extcon: Fix wrong index in max8997_extcon_cable[]

Currently, the index of "Dock-desk" and "Dock-card" are the same.
Thus the latter one overrides the first one.
Then we have problem when calling extcon_find_cable_index() because
edev->supported_cable[7] only matches "Dock-card".

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>