ARM: dts: msm: Add bus frequency definitions for CNSS in MSM8996

Add bus frequency definitions so that CNSS driver can vote for DDR
frequencies using these values which can help to achieve better power
as well as performance for WLAN in MSM8996 platform.

Change-Id: Ia5c3f5536414270c03ec726d31da05ccdb3293ad
Signed-off-by: Yue Ma <yuem@codeaurora.org>