clk: qcom: clk-alpha-pll: limit exported symbols to GPL licensed code

Unify all exported PLL clock configuration functions and data structures
as GPL symbols.

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>