board: sl28: add SATA support

board: sl28: add SATA support

Enable SATA support. Although not supported by the usual SATA pins on
the SMARC baseboard connector, SATA mode is supported on a PCIe lane.
This way one can use a mSATA card in a Mini PCI slot.

We need to invert the received data because in this mode the polarity of
the SerDes lane is swapped. Provide a fixup in board_early_init_f() for
the SPL. board_early_init_f() is then not common between SPL and u-boot
proper anymore, thus common.c is removed, as it just contained said
function.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>