TBBR authentication framework depends on the plat_get_rotpk_info()
function to return the pointer to the Root of Trust Public Key (ROTPK)
stored in the platform along with its length. Add this function for
RD-Daniel Config-XLR platform to support Trusted Board Boot. The
function makes use of the wrapper function provided by the arm common
trusted board boot function to get the ROTPK hash.

Change-Id: I509e2f7e88cc2167e1732a971d71dc131d3d4b01
Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>