ARM: dts: msm: remove contiguous etr memory reservation support for 8974

The TMC driver now uses dma_alloc_coherent api to allocate contiguous
memory instead of allocate_contiguous_ebi when configured for ETR. This
eliminates need to specify EBI memory reservation requirement, remove
the same from dt.

Change-Id: I689613002b65e7c84938f89ce9794d2a165d9aeb
Signed-off-by: Aparna Das <adas@codeaurora.org>