This patch adds a crypto driver which utilizes the ARM® TrustZone®
CryptoCell-712 to verify signature and hash during Trusted Board Boot. Along
with this driver, the CryptoCell SBROM library is required to successfully
build the BL image. The path to this library is specified via
the `CCSBROM_LIB_PATH` variable. Please note that, mbedTLS is still required
to do the X509 certificate ASN.1 parsing and CryptoCell is only utilized for
signature and hash verification.

Change-Id: If82dfbae0d7772ba1c64839f0b27850c103fe253
Signed-off-by: Soby Mathew <soby.mathew@arm.com>