common: Enable required U-Boot options in fragment file

This ensures that U-Boot images that we build can always:

- Rely on the environment extensions in env.dtsi being available
- Access the configured signing keys
- Use SD/eMMC cards
- Extract files from SquashFS filesystems

All of which are foundations that we intend to design our image
loading around.

board/common/uboot-extras.config

@@ -1,3 +0,0 @@
-CONFIG_DISTRO_DEFAULTS=y
-CONFIG_CMD_PXE=y
-

board/common/uboot/extras.config

@@ -0,0 +1,20 @@
+# CONFIG_OF_OMIT_DTB is not set
+CONFIG_DEVICE_TREE_INCLUDES="infix-env.dtsi infix-key.dtsi"
+
+CONFIG_ENV_IMPORT_FDT=y
+
+CONFIG_FIT=y
+CONFIG_FIT_SIGNATURE=y
+CONFIG_BLKMAP=y
+
+CONFIG_DISTRO_DEFAULTS=y
+CONFIG_CMD_SETEXPR_FMT=y
+
+CONFIG_MMC=y
+CONFIG_MMC_SDHCI=y
+CONFIG_MMC_PCI=y
+CONFIG_CMD_MMC=y
+
+CONFIG_FS_SQUASHFS=y
+CONFIG_CMD_SQUASHFS=y
+

configs/fireant_boot_defconfig

@@ -19,4 +19,4 @@ BR2_TARGET_UBOOT_CUSTOM_GIT=y
 BR2_TARGET_UBOOT_CUSTOM_REPO_URL="https://github.com/kernelkit/u-boot.git"
 BR2_TARGET_UBOOT_CUSTOM_REPO_VERSION="c3d9cdcc7d9e3eb490d4036f5eece3fb91a2485c"
 BR2_TARGET_UBOOT_BOARD_DEFCONFIG="mscc_fireant_pcb135_emmc"
-BR2_TARGET_UBOOT_CONFIG_FRAGMENT_FILES="$(BR2_EXTERNAL_INFIX_PATH)/board/common/uboot-extras.config"
+BR2_TARGET_UBOOT_CONFIG_FRAGMENT_FILES="$(BR2_EXTERNAL_INFIX_PATH)/board/common/uboot/extras.config"