ARM: dts: msm8974: Hook up adsp-pil's xo clock

Without this patch (and with CONFIG_QCOM_ADSP_PIL), I get this error:

	[    0.711529] qcom_adsp_pil adsp-pil: failed to get xo clock
	[    0.711540] remoteproc remoteproc0: releasing adsp-pil

With this patch, adsp-pil can initialize correctly.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>