ARM: dts: msm: Increase ADSP ION heap for SDA845 SVR platform

Increase ADSP ION heap to 300MB to allow for compute tasks to be
offloaded to DSP in VR usecase. The DSP to which the compute task is
being offloaded does not have a SMMU in front of it and hence require
the memory to be contiguous.

Change-Id: I2277de292fe3c25be4b61d1232dc80bd5c11d3fe
Signed-off-by: Sathish Ambley <sathishambley@codeaurora.org>