Fixed a possibly uninitialized value warning in the DMA code.
Fixed a possibly uninitialized value warning in the DMA code.

The `config` is set in an `else if` block, when it should be set in an
`else` block. Since it's based on a enum with only two values, the `else
if` is sufficient, but certain compilers may not recognize this,
throwing a error if `-Werror` is specified.

bperez77/xilinx_axidma