freescale: Remove CONFIG_DM from header files

Kconfig options must defined in the defconfig files. Since RSA_SOFTWARE_EXP
relies on CONFIG_DM, unless it is set in kconfig we cannot enable RSA.
Remove the hacks which enable CONFIG_DM in header files and update the
defconfig.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/P1010RDB-PB_NAND_SECBOOT_defconfig b/configs/P1010RDB-PB_NAND_SECBOOT_defconfig
index 51286af..0334353 100644
--- a/configs/P1010RDB-PB_NAND_SECBOOT_defconfig
+++ b/configs/P1010RDB-PB_NAND_SECBOOT_defconfig
@@ -1,7 +1,9 @@
 CONFIG_PPC=y
+# CONFIG_SYS_MALLOC_F is not set
 CONFIG_MPC85xx=y
 CONFIG_TARGET_P1010RDB=y
 CONFIG_SYS_EXTRA_OPTIONS="P1010RDB_PB,NAND_SECBOOT,SECURE_BOOT"
+CONFIG_DM=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_SPANSION=y
 CONFIG_NETDEVICES=y