clk: qcom: rpmh: Update the XO clock source for SC7280

The bi_tcxo clock source for SC7280 requires a div 4 to derive 19.2MHz
from the xo_board. Thus update the same.

Fixes: fff2b9a6

 ("clk: qcom: rpmh: Add support for RPMH clocks on SC7280")
Signed-off-by: Taniya Das <tdas@codeaurora.org>
Link: https://lore.kernel.org/r/1615400283-20100-1-git-send-email-tdas@codeaurora.org
Signed-off-by: Stephen Boyd <sboyd@kernel.org>