dt-bindings: memory-controllers: ti,gpmc: Add compatible for AM64

AM64 SoC contains the GPMC module. Add compatible for it.

Newer SoCs don't necessarily map GPMC data region at the same place
as legacy SoCs. Add reg-names "data", to provide this information to
the device driver.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211221131757.2030-2-rogerq@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>