flash/nor/core: adjust flash_iterate_address_range_inner() for 64-bit

flash/nor/core: adjust flash_iterate_address_range_inner() for 64-bit

Use target_addr_t exclusively for comparison of sector boudaries and
address range.

Use the last addres for both address range end and sector end.
It avoids problems with a flash bank mapped at the very end of
target address space.

Change-Id: Idf97c837453d97cbc4cf8a1c76ad799f4142f19e
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/4985
Tested-by: jenkins
Reviewed-by: Tim Newsome <tim@sifive.com>
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>