jtag: restore only if save has occurred

When power collapse is disabled, hotplug OFF of non-boot
core will result in WFI and hence msm_jtag_save_state
will not occur. Subsequently, during hotplug ON of
non-boot core when msm_jtag_restore_state is called via
msm_platform_secondary_init, we will now bail out without
restoring to help retain sane value of the restore counter
and prevent register restoration.

Change-Id: I9033f35e7307382b81603e9ff5aef8e2fd1bcbd9
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>