arm64: dts: freescale: ls1028a: Fix embedded PCI interrupt mapping

PCI devices should use PCI interrupt binding for their interrupts assuming
they function as standard PCI interrupts. The embedded PCI devices in the
LS1028a are mapping the interrupts directly to the host interrupt
controller. While that works here, it is unusual.

Based on the reference manual, there is not any INTC or INTD to map, so
only INTA and INTB are mapped.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>