imx: iomux-v3: Add iomux-mx53.h

Allow usage of the imx-common/iomux-v3.h framework by including pad settings for
the i.MX53. The content of the file is taken from Freescale's Linux kernel at
commit 4ab3715, plus the required changes to make it work in U-Boot.
Signed-off-by: NBenoît Thébaudeau <benoit.thebaudeau@advansee.com>