[DRA7][McASP] Add initial support

Add initial support for the Multichannel Audio Serial Port (McASP),
it consists of 'dump' and 'show' commands supported for all 8 instances
of McASP in Jacinto6.

Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Misael Lopez Cruz <misael.lopez@ti.com>
Update changelog and revision to v1.68

Major thing this time is the addition of DRA7 support. There is a
bunch of work remaining as well.. We will get to it in small chunks.

Hope Patrick is not disappointed with the work done.

Signed-off-by: Nishanth Menon <nm@ti.com>