nios2: map physical address to uncached virtual address

Add ioremap() to map physical address to uncached virtual
address. We need this to convert the reg address from the
device tree.

The order of headers inclusion in interrupts.c is changed
because common.h will include board header that contains
IO_REGION_BASE.

In the future, the IO_REGION_BASE should be decided from
the device tree.
tree

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Acked-by: Marek Vasut <marex@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>