ARM: dts: dra7: Enable workaround for errata i870 in PCIe host mode

Add ti,syscon-unaligned-access property to PCIe RC nodes to set
appropriate bits in CTRL_CORE_SMA_SW_7 register to enable workaround for
errata i870.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>