ARM: dts: qcom: Set right IRQ type to MHI interrupt

Set right IRQ type property for MHI interrupt, Without
this getting below warning during bootup

WARNING: drivers/irqchip/irq-gic.c:gic_irq_domain_translate
(gic_irq_domain_translate)
(irq_create_fwspec_mapping)
(irq_create_of_mapping)
(of_irq_get)
(__platform_get_irq_byname)
(platform_get_irq_byname)
(mhi_dev_probe).

Change-Id: I86b3cb88ebd297d16fa0c6a27e96870845a0077b