atmel_spi_transfer() would check speed_hz and fail if
the speed was changed in the transfer. After commit
"spi: make sure all transfer has proper speed set"
this would happen on all transfers.

Change speed_hz check to only fail if a lower speed
than max is requested.
Signed-off-by: NJoachim Eastwood <manabian@gmail.com>
Acked-by: NNicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>