ARM: dts: msm: limit number of fastrpc sessions on SLPI for 8150

Limit the maximum number of fastrpc sessions that can be spawned
on SLPI, in accordance with the remote subsystem's constraint on
the maximum number of threads.

Change-Id: If531c27219d5e15b5e3b36290e9178ad03eecc1d
Acked-by: Thyagarajan Venkatanarayanan <venkatan@qti.qualcomm.com>
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>