[meta-freescale] U-Boot preferred provider (dizzy)

[Nikolay Dimitrov]

Hi guys,

Is it needed to set both PREFERRED_PROVIDER_u-boot and
PREFERRED_PROVIDER_virtual/bootloader variables in my machine file?

This was the way done in Daisy, but now in Dizzy I see more boards are
only using PREFERRED_PROVIDER_u-boot. The latter obviously works, the
question is which is the right way to do it :D.

Regards,
Nikolay