board/b4860qds: Add support to make PCIe SATA work on B4860QDS

1) SerDes2 Refclks have been set properly to make
     PCIe SATA to work as it work on SerDes refclk of 100MHz
  2) Mask the SerDes's device reset request before changing
     the Refclks for SerDes1 and SerDes2 for PLL locks to
     happen properly, device reset request bit unmasked
     after SerDes refclks configuration

Signed-off-by: Shaveta Leekha <shaveta@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>