jazz: remove usage of isa_mem_base

Do assorted changes in memory-mapped rtc interface.

Also fix size of ISA I/O memory region, which should be 0x10000 bytes.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>