ARM: dts: msm: Disable EP initiated BW scaling on switch for sdxlemur

Some EPs are capable of initiating Gen switching request. This
capability is only required for direct attach. When these EPs
are connected to downstream ports of switch, disable this feature
by not creating BW scaling MHI event ring.

Change-Id: Ifdcd90329201f6a180cd8ddece671c7746e5c635