qcom_defconfig: enable OF_UPSTREAM_BUILD_VENDOR

A single U-Boot binary can be run on many different Qualcomm boards just
by booting with a different DTB.

Simplify the build process for this by enabling OF_UPSTREAM_BUILD_VENDOR
so that all the DTBs will be available after building U-Boot once.

Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Christopher Obbard <christopher.obbard@linaro.org>
Link: https://lore.kernel.org/r/20250328104011.1837872-1-caleb.connolly@linaro.org
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
diff --git a/configs/qcom_defconfig b/configs/qcom_defconfig
index ba4d38d..a12a5d1 100644
--- a/configs/qcom_defconfig
+++ b/configs/qcom_defconfig
@@ -41,6 +41,7 @@
 CONFIG_CMD_REGULATOR=y
 CONFIG_CMD_LOG=y
 CONFIG_OF_LIVE=y
+CONFIG_OF_UPSTREAM_BUILD_VENDOR=y
 CONFIG_USE_DEFAULT_ENV_FILE=y
 CONFIG_DEFAULT_ENV_FILE="board/qualcomm/default.env"
 CONFIG_BUTTON_QCOM_PMIC=y