hw/i2c/aspeed: Add support for 64 bit addresses

hw/i2c/aspeed: Add support for 64 bit addresses

ASPEED AST2700 SOC is a 64 bits quad core CPUs (Cortex-a35)
and the base address of dram is "0x4 00000000" which
is 64bits address.

The AST2700 support the maximum DRAM size is 8 GB.
The DRAM physical address range is from "0x4_0000_0000" to
"0x5_FFFF_FFFF".

The DRAM offset range is from "0x0_0000_0000" to
"0x1_FFFF_FFFF" and it is enough to use bits [33:0]
saving the dram offset.

Therefore, save the high part physical address bit[1:0]
of Tx/Rx buffer address as dma_dram_offset bit[33:32].
It does not need to decrease the dram physical
high part address for DMA operation.
(high part physical address bit[7:0] – 4)

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>