Revert "imx: defconfig: Enable CONFIG_SPL_FORCE_MMC_BOOT"

CONFIG_SPL_FORCE_MMC_BOOT was removed in a previous patch as its
behavior is the correct one in all cases.  Remove all uses of it from
defconfigs.

This reverts commit 3201e5b444ae3a13aa31e8b5101ad38d7ff0640d and removes
CONFIG_SPL_FORCE_MMC_BOOT from the imx28_xea defconfig.

Signed-off-by: Harald Seiler <hws@denx.de>
diff --git a/configs/display5_defconfig b/configs/display5_defconfig
index 4e10efd..6241375 100644
--- a/configs/display5_defconfig
+++ b/configs/display5_defconfig
@@ -39,7 +39,6 @@
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_SAVEENV=y
 CONFIG_SPL_I2C_SUPPORT=y
-CONFIG_SPL_FORCE_MMC_BOOT=y
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SPL_WATCHDOG_SUPPORT=y
diff --git a/configs/imx28_xea_defconfig b/configs/imx28_xea_defconfig
index e23d77d..d4feb66 100644
--- a/configs/imx28_xea_defconfig
+++ b/configs/imx28_xea_defconfig
@@ -30,7 +30,6 @@
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0
 CONFIG_SUPPORT_EMMC_BOOT_OVERRIDE_PART_CONFIG=y
 CONFIG_SPL_DMA=y
-CONFIG_SPL_FORCE_MMC_BOOT=y
 CONFIG_SPL_MMC_TINY=y
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SPL_SPI_LOAD=y