[PATCH] powerpc: Remove ItLpRegSave area from the paca

On iSeries, the paca contains, amongst other things an ItLpRegSave
structure used by the hypervisor to save registers.  The hypervisor
locates this area through a pointer at the beginning of the paca, so
the structure itself can be located elsewhere.  This patch moves the
reg_save area out into its own array.  This reduces the amount of
iSeries specific gunk which is visible to general powerpc code via
paca.h

Built and booted on POWER5 LPAR and iSeries RS64.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>