block: systemace: Added missing "else" in "ace_writew"

System ACE compact flash controller supports either 8-bit (default) or
16-bit data transfers. And in corresponding driver we need to implement
read/write of 16-bit data words properly for both modes of operation.

In existing code if width==8 both branches get executed which may cause
unexpected behavior of SystemAce controller.

Addition of "else" fixes described issue and execution is done as
expected for both (8-bit and 16-bit) data bus widths.

Signed-off-by: Alexey Brodkin <alexey.brodkin@gmail.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>