fastboot: mmc: Add CONFIG_FASTBOOT_MMC_USER_SUPPORT

Split userdata and boot partition support for eMMC update
and correct the description (update is supported).

The new configuration CONFIG_FASTBOOT_MMC_USER_SUPPORT
allows to activate support of userdata partition update,
based on target name=CONFIG_FASTBOOT_MMC_USER_NAME

This patch also removes the unnecessary dependency with
ARCH_MEDIATEK and EFI_PARTITION.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/configs/mt8518_ap1_emmc_defconfig b/configs/mt8518_ap1_emmc_defconfig
index b95d2c6..d5fb0cc 100644
--- a/configs/mt8518_ap1_emmc_defconfig
+++ b/configs/mt8518_ap1_emmc_defconfig
@@ -25,6 +25,7 @@
 CONFIG_FASTBOOT_FLASH=y
 CONFIG_FASTBOOT_FLASH_MMC_DEV=0
 CONFIG_FASTBOOT_MMC_BOOT1_SUPPORT=y
+CONFIG_FASTBOOT_MMC_USER_SUPPORT=y
 CONFIG_DM_MMC=y
 CONFIG_MMC_HS200_SUPPORT=y
 CONFIG_MMC_MTK=y