clk: qcom: common: Return NULL from clk_hw OF provider

Return NULL in the cases where the clk_hw is not registered with the
clock provider, but the clock consumer still requests for a clock id.

Signed-off-by: Taniya Das <tdas@codeaurora.org>
Link: https://lkml.kernel.org/r/20191014102308.27441-3-tdas@codeaurora.org


Signed-off-by: Stephen Boyd <sboyd@kernel.org>