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>

misc: Appease GCC 8

GCC 8 adds a number of new warnings to -Wall which generate errors.

- Fix memset to 0 for structs by adding casts.
- Fix cast with const when the const was ignored.
- Fix catch a polymorphic type by value

We now compile with GCC 8!

Change-Id: Iab70ce11190eee67608fc25c0bedff170152b153
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/11949
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

dev: Make the IDE controller handle NULL simobject pointers.

Only panic if there are disks which would actually be connected to it beyond
its limit. Also skip past disks which are set to NULL. This is useful since
it lets you set up disks on different ports of the controller instead of
filling them contiguously.

Change-Id: I92f1316d3ad6931e25bfffeb34fb2603c0b95ce7
Reviewed-on: https://gem5-review.googlesource.com/4848
Maintainer: Gabe Black <gabeblack@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

dev: Fix an IDE error check.

The error message says an IDE controller can support at most 4 disks, but the
check would fail if there were more than 3 disks.

Change-Id: Ic7d5d8c941fe2580da43019f53991377d4727bb9
Reviewed-on: https://gem5-review.googlesource.com/4460
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

dev: Move storage devices to src/dev/storage/

Move the IDE controller and the disk implementations to
src/dev/storage.