arm64: dts: qcom: msm8998: Fixup clock to use xo_board

This patch sets the msm8998 xo clock name back to xo_board.  Recent
clock tree changes fixed the clock tree and the change to the xo name
is causing issues where msm8998 boards do not boot properly.  Let's
change it back and leave the xo label on it.

Fixes: 634da330 (arm64: dts: qcom: msm8998: correct xo clock name)
Signed-off-by: Andy Gross <andy.gross@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org>