clk: qcom: gcc-sm6375: Ensure unsigned long type

This PLL frequency needs a UL postfix to avoid compiler warnings on
32-bit architectures.

Fixes: 184fdd87 ("clk: qcom: Add global clock controller driver for SM6375")
Cc: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>