BugLink: http://bugs.launchpad.net/bugs/1537881
https://lists.ozlabs.org/pipermail/linuxppc-dev/2016-January/138009.html

OPAL_CALL wrapper code sticks the r1 (stack pointer) into PACAR1 purely
for debugging purpose only. The power7_wakeup* functions relies on stack
pointer saved in PACAR1. Any opal call made using opal wrapper (directly
or in-directly) before we fall through power7_wakeup*, then it ends up
replacing r1 in PACAR1(r13) leading to kernel panic. So far we don't see
any issues because we have never made any opal calls using OPAL wrapper
before power7_wakeup*. But the subsequent HMI patch would need to invoke
C calls during cpu wakeup/idle path that in-directly makes opal call using
opal wrapper. This patch facilitates the subsequent HMI patch by removing
usage of PACAR1 from opal call wrapper.
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>