[media] rc: img-ir: Add and enable sys clock for img-ir

Gets a handle to the system clock, already described in the binding
document, and calls the appropriate common clock framework functions
to mark it prepared/enabled, the common clock framework initially
enables the clock and doesn't disable it at least until the
device/driver is removed.
It's important the systen clock is enabled before register interface is
accessed by the driver.
The system clock to IR is needed for the driver to communicate with the
IR hardware via MMIO accesses on the system bus, so it must not be
disabled during use or the driver will malfunction.

Signed-off-by: Sifan Naeem <sifan.naeem@imgtec.com>
Acked-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>