configs/solidrun_clearfog: bump U-Boot to 2019.07

Fixes "SPL image too big" error.

Fixes:
https://gitlab.com/buildroot.org/buildroot/-/jobs/269139293

Cc: Jan Kundrát <jan.kundrat@cesnet.cz>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

configs/solidrun_clearfog_defconfig

@@ -33,7 +33,7 @@ BR2_PACKAGE_HOST_GENIMAGE=y
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
-BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2018.11"
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2019.07"
 BR2_TARGET_UBOOT_BOARD_DEFCONFIG="clearfog"
 BR2_TARGET_UBOOT_NEEDS_DTC=y
 BR2_TARGET_UBOOT_NEEDS_OPENSSL=y