dev: Explicitly specify the endianness for packet accessors.

Generally speaking, the endianness of the data devices provide or
accept is dependent on the device and not the ISA the system
executes. This change makes the devices in dev pick an endianness
rather than using the guest's.

For the ISA bus and the UART, accesses are byte sized and so endianness
doesn't matter. The ISA and PCI busses and the devices which use them
are defined to be little endian.

Change-Id: Ib0aa70f192e1d6f3b886d9f3ad41ae03bddb583f
Reviewed-on: https://gem5-review.googlesource.com/c/13462
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

dev-arm: Fix the address range for some I/O devices

Previously, many devices were incorrecty configured to respond to an
address range of size 0xfff. This changes fixes this and sets it to
0x1000.

Change-Id: I4b027a27adf60ceae4859e287d7f34443b398752
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/11116
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

dev: Move i2c functionality to src/dev/i2c/