juno_hdlcd: Add support for HDLCD clocks

This patch adds the support to manage the HDLCD clocks.
For the Juno board. It is expected that this module uses
the juno_cdcel937 module as its driver.

Change-Id: Icefeded7701b917909ad62c0bb4377034292f31a
Signed-off-by: Elieva Pignat <Elieva.Pignat@arm.com>
Signed-off-by: Jim Quigley <jim.quigley@arm.com>
Signed-off-by: Raphael Gault <raphael.gault@arm.com>