Not all remote processors employ an IOMMU, so do not error out
on !iommu_present().

Note: we currently still use iommu_present() to tell whether we need
to configure an IOMMU or not. That works for simple cases, but will
easily fail with more complicated ones (e.g. where an IOMMU exists,
but not all remote processors use it). When those use cases show up,
we will solve them by introducing something like remoteproc hw
capabilities.

[ohad@wizery.com: write commit log]
Signed-off-by: NMark Grosen <mgrosen@ti.com>
Signed-off-by: NOhad Ben-Cohen <ohad@wizery.com>

Modern SoCs typically employ a central symmetric multiprocessing (SMP)
application processor running Linux, with several other asymmetric
multiprocessing (AMP) heterogeneous processors running different instances
of operating system, whether Linux or any other flavor of real-time OS.

Booting a remote processor in an AMP configuration typically involves:
- Loading a firmware which contains the OS image
- Allocating and providing it required system resources (e.g. memory)
- Programming an IOMMU (when relevant)
- Powering on the device

This patch introduces a generic framework that allows drivers to do
that. In the future, this framework will also include runtime power
management and error recovery.

Based on (but now quite far from) work done by Fernando Guzman Lugo
<fernando.lugo@ti.com>.

ELF loader was written by Mark Grosen <mgrosen@ti.com>, based on
msm's Peripheral Image Loader (PIL) by Stephen Boyd <sboyd@codeaurora.org>.

Designed with Brian Swetland <swetland@google.com>.
Signed-off-by: NOhad Ben-Cohen <ohad@wizery.com>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Cc: Brian Swetland <swetland@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg KH <greg@kroah.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>