imx: iomux: add macros to setup iomux for multiple SoC types

Allow imx_iomux_v3_setup_multiple_pads to take a multi-cpu pad_list
and add macros for declaring the pad_list that take into account the
SoC types supported using CONFIG_MX6QDL (supports both the MX6Q and MX6DL
iomux).

Cc: Stefan Roese <sr@denx.de>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Andy Ng <andreas2025@gmail.com>
Cc: Eric Nelson <eric.nelson@boundarydevices.com>
Cc: Tapani Utriainen <tapani@technexion.com>
Cc: Tom Rini <trini@ti.com>

Signed-off-by: Tim Harvey <tharvey@gateworks.com>