ARM: dts: msm: reduce rx ring sizes for MDM9640

Reduce RX ring sizes to 192 to avoid memory allocation
failures.

Change-Id: Id1a957a41d6482df5c3ded2844a13526f1e34ee2
CRs-Fixed: 1050748
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>