toradex: imx6: Rework PF0100 fuse programming commands to not be in SPL

The code for programming the OTP fuses on the PMIC PF0100 can only be
used in full U-Boot, so do not build / link it into SPL.

Cc: Max Krummenacher <max.krummenacher@toradex.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Max Krummenacher <max.krummenacher@toradex.com>