clk: qcom: gcc-msm8996: drop unsupported clock sources

In preparation of updating the msm8996 gcc driver, drop all unsupported
GPLL sources (gpll1/gpll1_early_div, gpll2/gpll2_early and gpll3).
Downstream kernel also does not provide support for these GPLL sources,
so it is safe to drop them.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211228045415.20543-14-dmitry.baryshkov@linaro.org