ahci: change 'masking port_map' printk to KERN_WARNING level

It's not so much an error as a warning about normal Marvell crazines.
So don't use KERN_ERR that ends up spamming the console even in quiet
mode, it's not _that_ critical.

Explained by Jeff:

 "Long explanation, it's a mess:

  Marvell took standard AHCI, and bastardized it to include a weird mode
  whereby PATA devices appear inside the AHCI DMA and interrupt
  infrastructure you're familiar with.

  So, PATA devices appear via pata_marvell driver, using basic legacy
  IDE programming interface.  But SATA devices, which might also be
  attached to this chip, either work in under-performing mode or
  simply don't work at all (e.g.  newer 6 Gbps devices or port
  multiplier attachments, NCQ, ...)

  On the other hand, 'ahci' driver loads and works with the chip's
  attached SATA devices quite beautifully, but is completely unable to
  drive any attached PATA devices, due to the Marvell-specific
  PATA-under-AHCI interface.

  The "masking port_map 0x7 -> 0x3" message is the ahci driver "hiding"
  the PATA port(s) from itself, making sure it will only drive the SATA
  ports it knows how to drive."

Acked-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>