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In preparation for adding support for Reference Design platforms
which have different base addresses for GIC Distributor or
Redistributor, move GIC related base addresses to individual platform
definition files.

Change-Id: Iecf52b4392a30b86905e1cd047c0ff87d59d0191
Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>