cpuidle: lpm-levels: Save restore jtag registers for 8996

Jtag registers are lost when the CPUs are power collapsed.
Without save restore of these registers ETM tracing may
not work properly. Save restore jtag registers across CPU
power collapses.

Change-Id: If12105602fa0d1d6911077a29dfe3d870fec261f
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>