xen/arm: Add support for GIC v3

Add support for GIC v3 specification System register access(SRE)
is enabled to access cpu and virtual interface regiseters based
on kernel GICv3 driver.

This patch adds only basic v3 support.
Does not support Interrupt Translation support (ITS)

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
xen/arm: Add virtual GICv3 support

Add virtual GICv3 driver support.
Also, with this patch vgic_irq_rank structure is modified to
hold GICv2 GICD_TARGET and GICv3 GICD_ROUTER registers under
union.

This patch adds only basic GICv3 support.
Does not support Interrupt Translation support (ITS)

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
xen/arm: Update Dom0 GIC dt node with GICv3 information

Update GIC device tree node for DOM0 with GICv3
information. GIC hw specfic device tree information
is moved to respective GIC driver.

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
xen/arm: add SGI handling for GICv3

In ARMv8, write to ICC_SGI1R_EL1 register raises trap to EL2.
Handle the trap and inject SGI to vcpu.

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
xen/arm: check for GICv3 platform support

ID_AA64PFR0_EL1 register provides information about GIC support.
Check for this register in GICv3 driver.

Also print GICv3 support information in boot log

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>