arm64/dtsi: move xhci_dma to DMA coherent region

CMA could be allocated from zram, move the xhci_dma reserved memory from
CMA to DMA coherent region.

Bug: 195433739
Test: build and boot pass
Change-Id: I37d218322e81922d2bdd6f8597b221a66007cdb3
Signed-off-by: Howard Yen <howardyen@google.com>