openamp shared memory regions can be anywhere in DDR memory
withing 2G range. Current SRAM_PRIV region is 64M which
prevents access of shared memory (vrings) by RPU (cortex-r5)
if it is out of 64M range. This patch allows vrings to be in DDR within
2G address space.

Developed-by: Dan Millea
Commited by: Tanmay Shah

Signed-off-by: Dan Milea <dan.milea@windriver.com>
Signed-off-by: Tanmay Shah <tanmay.shah@amd.com>

Add ipm driver to use Inter Processor Interrupts
on Xilinx ZynqMP platform. This patch also adds sample
application that shows use of xlnx ipm driver.

This driver uses default arm gic interrupt controller
and works only for lockstep mode of cortex-r5f
cluster for now.

In split mode the cortex-r5 cluster will
have two r5f cores and they are expected to work in AMP
mode. If both r5f cores run simultaneouly, only one of
the core is able to receive IPI interrupts at this time
and it will be the one that started later. In future
this limitation shall be removed.

Signed-off-by: Tanmay Shah <tanmay.shah@amd.com>