ARM: imx: Remove mach-mxt_td60 board file

All the current support of mach-mxt_td60 board can be converted to devicetree.

Remove the board file.

Cc: Alan Carvalho de Assis <acassis@gmail.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>