Allow SPL to be built with this option so that we can support device tree
control. Disable the simple bus for now in SPL. It may be needed later.

Signed-off-by: Simon Glass <sjg@chromium.org>

For SPL we don't expect to need to remove a device. Save some code space
by dropping this feature. The board config can define
CONFIG_DM_DEVICE_REMOVE if this is in fact needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@ti.com>

Add a driver for the simple-bus nodes, which allows devices within these
nodes to be bound.

Signed-off-by: Simon Glass <sjg@chromium.org>

[1] Move driver/core/, driver/input/ and drivers/input/ entries
    from the top Makefile to drivers/Makefile

[2] Remove the conditional by CONFIG_DM in drivers/core/Makefile
    because the whole drivers/core directory is already selected
    by CONFIG_DM in the upper level

[3] Likewise for CONFIG_DM_DEMO in drivers/demo/Makefile

[4] Simplify common/Makefile - both CONFIG_DDR_SPD and
    CONFIG_SPD_EEPROM are boolean macros so they can directly
    select objects

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Marek Vasut <marex@denx.de>

Add driver model functionality for generic board.

This includes data structures and base code for registering devices and
uclasses (groups of devices with the same purpose, e.g. all I2C ports will
be in the same uclass).

The feature is enabled with CONFIG_DM.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Pavel Herrmann <morpheus.ibis@gmail.com>
Signed-off-by: Viktor Křivák <viktor.krivak@gmail.com>
Signed-off-by: Tomas Hlavacek <tmshlvck@gmail.com>