remoteproc/omap: set bootaddr support

Some remote processors (like OMAP4's DSP) require we explicitly
set a boot address from which they'd start executing code when
taken out of reset.

Support for this is now being added to the omap-specific remoteproc
driver through a set_bootaddr function in the platform data which,
if needed, must be set according to the backend remote processor.

For OMAP4's dsp we can use the following control function:

  .set_bootaddr  = omap_ctrl_write_dsp_boot_addr

Signed-off-by: Juan Gutierrez <jgutierrez@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
[ohad: slight changes to the commit log]
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>