configs: am57xx_evm_defconfig: Enable 'dtimg' command

We are going to implement DTBO partition for BeagleBoard X15 further. To
support this, 'dtimg' command must be enabled.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
diff --git a/configs/am57xx_evm_defconfig b/configs/am57xx_evm_defconfig
index a1b8d2d..96de6f4 100644
--- a/configs/am57xx_evm_defconfig
+++ b/configs/am57xx_evm_defconfig
@@ -28,6 +28,7 @@
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SPL_YMODEM_SUPPORT=y
+CONFIG_CMD_DTIMG=y
 CONFIG_CMD_SPL=y
 CONFIG_CMD_BCB=y
 # CONFIG_CMD_FLASH is not set