Revert "msm: adsprpc: DSP device node to provide restricted access to ADSP/SLPI"

Applicable only for CDSP present branches. Not needed for 4.4 kernel.

This reverts commit 90cb306f.

Change-Id: I645120212b2c9a43cb5d12cc866d5592979cd44b
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>