target-ppc: Introduce callback for interrupt endianness

target-ppc: Introduce callback for interrupt endianness

POWER7, POWER7+ and POWER8 families use the ILE bit of the LPCR
special purpose register to decide the endianness to use when
entering interrupt handlers. When running a Linux guest, this
provides a hint on the endianness used by the kernel. And when
it comes to dumping a guest, the information is needed to write
ELF headers using the kernel endianness.

Suggested-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
[agraf: change subject line]
Signed-off-by: Alexander Graf <agraf@suse.de>