mx6q: mx6qsabrelite: Conditionally define macros for environment in serial flash

mx6q: mx6qsabrelite: Conditionally define macros for environment in serial flash

The default settings store the persistent environment on SD card
and not serial flash (SPI NOR).

To use SPI NOR to save the environment instead of SD card, edit
include/configs/mx6qsabrelite.h and

- undefine CONFIG_ENV_IS_IN_MMC
- define   CONFIG_ENV_IS_IN_SPI_FLASH

The SPI driver can take as chip select the controller's chip selects
as well as an external GPIO. The LSB byte has the value of the internal
chip select, the highest (thought as 16-bit value) contains the GPIO
number.

The GPIO used on Sabre Lite is GP3:19 == 83.

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
Acked-by: Jason Liu <jason.hui@linaro.org>
Tested-by: Jason Liu <jason.hui@linaro.org>