ioemu, passthrough: fix writing handlers for base address registers.

ioemu, passthrough: fix writing handlers for base address registers.

This patch fixes writing handlers for base address registers (include
expansion rom base address register) as follows.
It can be applied to both ioemu-remote and ioemu.

- Current implementation can not work fine when base address registers
  are accessed via 1 byte write access and 2 byte write access. This
  patch enables them.

- Currently guest software can set address which is not aligned
  with resource size and page size. The patch does not allow guest
  software to set unaligned address.

Signed-off-by: Yuji Shimada <shimada-yxb@necst.nec.co.jp>