[media] s5p-fimc: Add device tree based sensors registration

[media] s5p-fimc: Add device tree based sensors registration

The sensor (I2C and/or SPI client) devices are instantiated by their
corresponding control bus drivers. Since the I2C client's master clock
is often provided by a video bus receiver (host interface) or other
than I2C/SPI controller device, the drivers of those client devices
are not accessing hardware in their driver's probe() callback. Instead,
after enabling clock, the host driver calls back into a sub-device
when it wants to activate them. This pattern is used by some in-tree
drivers and this patch also uses it for DT case. This patch is intended
as a first step for adding device tree support to the S5P/Exynos SoC
camera drivers. The second one is adding support for asynchronous
sub-devices registration and clock control from sub-device driver
level. The bindings shall not change when asynchronous probing support
is added.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>