sparc64: fix for user probes in high memory

sparc64: fix for user probes in high memory

Orabug 25428066

When returning from the user probe code into userspace process, PC & NPC are
truncated to 32 bits.

As a result of shared libraries get loaded very high in the virtual address
space of the process, placing a user probe inside a shared library makes the
kernel return into the process at the wrong address, causing it to seg'fault
most of the time.

This patch prevents truncating PC and NPC.

Signed-off-by: Eric Saint Etienne <eric.saint.etienne@oracle.com>
Reviewed-by: David Aldridge <david.j.aldridge@oracle.com>
Signed-off-by: Allen Pais <allen.pais@oracle.com>