configs: add qcm6490_defconfig

Introduce a defconfig for the RB3 Gen 2 and other QCM6490 boards with a
dedicated uefi partition. These can replace EDK2 entirely with U-Boot.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index daaf034..7ab39d9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -617,6 +617,7 @@
 L:	u-boot-qcom@groups.io
 S:	Maintained
 T:	git https://source.denx.de/u-boot/custodians/u-boot-snapdragon.git
+F:	configs/qcm6490_defconfig
 F:	drivers/*/*/pm8???-*
 F:	drivers/gpio/msm_gpio.c
 F:	drivers/mmc/msm_sdhci.c