Move existing use of CONFIG_SPL_DM to Kconfig

Move existing use of CONFIG_SPL_DM to Kconfig

A few boards define this in a header file which is incorrect. It means that
Kconfig options that rely on this cannot be used. Move it.

Note that quite a few boards defined this options but do not appear to
actually use SPL:

	BSC9132QDS_NOR_DDRCLK100_SECURE
	BSC9132QDS_NOR_DDRCLK133_SECURE
	BSC9132QDS_SDCARD_DDRCLK100_SECURE
	BSC9132QDS_SDCARD_DDRCLK133_SECURE
	BSC9132QDS_SPIFLASH_DDRCLK100_SECURE
	BSC9132QDS_SPIFLASH_DDRCLK133_SECURE
	C29XPCIE_NOR_SECBOOT
	P1010RDB-PA_36BIT_NAND_SECBOOT
	P1010RDB-PA_36BIT_SPIFLASH_SECBOOT
	P1010RDB-PA_NAND_SECBOOT
	P1010RDB-PA_NOR_SECBOOT
	P1010RDB-PB_36BIT_NOR_SECBOOT
	P1010RDB-PB_36BIT_SPIFLASH_SECBOOT
	P1010RDB-PB_NAND_SECBOOT
	P1010RDB-PB_NOR_SECBOOT
	P3041DS_SECURE_BOOT
	P4080DS_SECURE_BOOT
	P5020DS_NAND_SECURE_BOOT
	P5040DS_SECURE_BOOT
	T1023RDB_SECURE_BOOT
	T1024QDS_DDR4_SECURE_BOOT
	T1024QDS_SECURE_BOOT
	T1024RDB_SECURE_BOOT
	T1040RDB_SECURE_BOOT
	T1042D4RDB_SECURE_BOOT
	T1042RDB_SECURE_BOOT
	T2080QDS_SECURE_BOOT
	T2080RDB_SECURE_BOOT
	T4160QDS_SECURE_BOOT
	T4240QDS_SECURE_BOOT
	ls1021aqds_nor_SECURE_BOOT
	ls1021atwr_nor_SECURE_BOOT
	ls1043ardb_SECURE_BOOT

For these boards CONFIG_SPL_DM will no-longer be defined in SPL. But since
they apparently don't have an SPL, this should not matter.

Signed-off-by: Simon Glass <sjg@chromium.org>