freescale/qixis: Add support for booting from SD/QSPI

freescale/qixis: Add support for booting from SD/QSPI

1.Use "qixis_reset sd" to boot from SD
2.Use "qixis_reset sd_qspi" to boot from SD with QSPI support
3.Use "qixis_reset qspi" to boot from QSPI flash

On some SoCs such as LS1021A and LS1043A, IFC and QSPI could be
pin-multiplexed. So the switches are different between SD boot with
IFC support and SD boot with QSPI support. The default booting from
SD is with IFC support.

Once QSPI is enabled(IFC disabled), only use I2C to access QIXIS.

Signed-off-by: Gong Qianyu <Qianyu.Gong@freescale.com>
Reviewed-by: York Sun <york.sun@nxp.com>