clk: qcom: clk-pll: Round off req_rate in determine rate

The current PLL set rate does not support determining
the L val at runtime. This updates the determine rate
by doing round off for this requirement. Add support
for the list_register to clk_pll_ops.

Change-Id: Ica85e1408fd7d1b2154b01150728419dbb81de90
Signed-off-by: Chetan C R <cchinnad@codeaurora.org>