nitrogen6_max: re-work I2C initialization

It's much easier to validate i.MX6DQ/i.MX6DLS settings
for each bus with them in a single array.

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
nitrogen6_max: Update SPI NOR to match updates in main-line

Default chip-select is done in a call-back, doesn't need
SPI pad control.

See commits 155fa9af9 and 3b31605ae.

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
nitrogen6_max: board file supports all i.MX6 variants, config only i.MX6Q

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>