This patch cleans up the use of dma_get_required_mask and uses the
simpler dma_set_mask_and_coherent function instead of doing these as
separate steps.

I removed the dma_get_required_mask call because based on some minimal
testing it appears that either (a) we're not doing the right thing with
the call or (b) we don't need it anyways. If the value returned is
<48bits, we'll end up trying with 48 bits anyways. If it's over 48bits,
fm10k can't support that anyways, and we should try 48bits. If 48bits
fails, we'll fallback to 32bits. This cleans up some very funky code.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>