freescale: Ensure common commands are not included in SPL binary

Both the "qixis_reset" and esbc_validate" commands can only be used in
full U-Boot so do not build them in SPL.  As part of this rework the
qixis code to declare things as static and make use of __weak for
function aliases.

Cc; York Sun <york.sun@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: York Sun <york.sun@nxp.com>