drm/msm: dsi: dev_pm_opp_put_clkname() only when an opp_table exists

Its possible for msm_dsi_host_init() to fail early, before
dev_pm_opp_set_clkname() is called. In such cases, unconditionally
calling dev_pm_opp_put_clkname() in msm_dsi_host_destroy() results
in a crash. Put an additional check so that dev_pm_opp_put_clkname()
is called only when an opp_table exists.

Fixes: f99131fa7a23 ("drm/msm: dsi: Use OPP API to set clk/perf state")
Reported-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>