devm_of_clk_add_hw_provider() may return an errno, so
add a return value check

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 8410e7f3 ("cpufreq: scmi: Fix OPP addition failure with a dummy clock provider")
Signed-off-by: Alexandra Diupina <adiupina@astralinux.ru>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>