PM: Fix a bug in dpm_suspend_late()

If there is any error while executing "late suspend" callbacks, then
the pm_runtime_enable() will not be called.
Hence in case of an error call pm_runtime_enable() before exiting from
dpm_suspend_late().

CRs-fixed: 740511
Change-Id: Iedacbbf47a4ef0ab0a0ace71fc809d056d56f89f
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>