ARM: dts: msm: Add interrupt property support for SDX20

MHI driver has individual interrupt supported in SDX20.
Add DT property such that PCIe will not configure for a7
interrupt.

Change-Id: I6176c57906335ac35d48915304f84e6aff024423
Signed-off-by: Rama Krishna Phani A <rphani@codeaurora.org>