feat(plat/arm): improve dram bank lookup

Next generation neoverse reference designs, such as RD-V3, can have
more than two non-contiguous DRAM banks. On such platforms, these
banks are spread across the system memory map.

This change modifies the common platform granule handlers to more
efficiently translate address-to-index and index-to-address on
platforms with a large number of DRAM banks. To support this arm
platforms have now have a common config option to select the
maximum number of DRAM banks - PLAT_ARM_MAX_DRAM_BANKS.

Change-Id: I6d5b02f8d3052d6b189f21ef48d1f684acb63b86
Signed-off-by: Harry Moulton <harry.moulton@arm.com>
Signed-off-by: Vivek Gautam <vivek.gautam@arm.com>