nitrogen6x: README: Only calling 'make' is enough

No need to pass 'u-boot.imx' as parameter for 'make' because u-boot.imx is
built by default.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Eric Nelson <eric.nelson@boundarydevices.com>
1 file changed