rockchip: rk3399-puma: support Gigadevice SPI-NOR flash

rockchip: rk3399-puma: support Gigadevice SPI-NOR flash

Over the last quarter, a part of our production has used NOR flash
from Gigadevice in addition to the Winbond parts that we typically
source.  This requires the SPI_FLASH_GIGADEVICE config to be set.

Enable SPI_FLASH_GIGADEVICE in the board's default defconfig.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Klaus Goger <klaus.goger@theobroma-systems.com>