dm: spl: Allow device tree/driver model in board_init_f()

Add an spl_init() function that does basic init such that board_init_f() can
use simple malloc(), device tree and driver model. Each one is set up only
if enabled for SPL.

Note: We really should refactor SPL such that there is a single
board_init_f() and rename the existing weak board_init_f() functions
provided by boards, calling them from the single board_init_f().

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
index db0550b..7ef3e25 100644
--- a/include/asm-generic/global_data.h
+++ b/include/asm-generic/global_data.h
@@ -116,5 +116,6 @@
 #define GD_FLG_ENV_READY	0x00080	/* Env. imported into hash table   */
 #define GD_FLG_SERIAL_READY	0x00100	/* Pre-reloc serial console ready  */
 #define GD_FLG_FULL_MALLOC_INIT	0x00200	/* Full malloc() is ready	   */
+#define GD_FLG_SPL_INIT		0x00400	/* spl_init() has been called	   */
 
 #endif /* __ASM_GENERIC_GBL_DATA_H */