of: fdt: Aggregate the processing of "linux,usable-memory-range"

of: fdt: Aggregate the processing of "linux,usable-memory-range"

Currently, we parse the "linux,usable-memory-range" property in
early_init_dt_scan_chosen(), to obtain the specified memory range of the
crash kernel. We then reserve the required memory after
early_init_dt_scan_memory() has identified all available physical memory.
Because the two pieces of code are separated far, the readability and
maintainability are reduced. So bring them together.

Suggested-by: Rob Herring <robh@kernel.org>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
(change the prototype of early_init_dt_check_for_usable_mem_range(), in
order to use it outside)
Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Tested-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Acked-by: John Donnelly <john.p.donnelly@oracle.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
To: devicetree@vger.kernel.org
To: linux-efi@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>