ARM: davinci: da8xx: add remoteproc support

Add remoteproc platform device for controlling the DSP
on da8xx. The patch uses CMA-based reservation of physical
memory block for DSP use. A new kernel command-line parameter
has been added to allow boot-time specification of the physical
memory block.

Signed-off-by: Robert Tivy <rtivy@ti.com>
[nsekhar@ti.com: edit commit message for readability and
style improvements]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>