fix(rdv3r1): add console name to checksum calculation on RD-V3-R1

The name field of console_info structure was missed in
checksum calculation. This is corrected by adding a new
helper checksum_calc() which computes the checksum in a
field agnostic manner.

Signed-off-by: Jerry Wang <Jerry.Wang4@arm.com>
Change-Id: I318379f3a64f26b7f84c6d162d2d5a3085f5c9a0