OMAP3 SPL: Add identify_nand_chip function

A number of boards are populated with a PoP chip for both DDR and NAND
memory.  Other boards may simply use this as an easy way to identify
board revs.  So we provide a function that can be called early to reset
the NAND chip and return the result of NAND_CMD_READID.  All of this
code is put into spl_id_nand.c and controlled via CONFIG_SPL_OMAP3_ID_NAND.

Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/arch/arm/include/asm/arch-omap3/sys_proto.h b/arch/arm/include/asm/arch-omap3/sys_proto.h
index 80e167b..e5031d5 100644
--- a/arch/arm/include/asm/arch-omap3/sys_proto.h
+++ b/arch/arm/include/asm/arch-omap3/sys_proto.h
@@ -40,6 +40,7 @@
 void do_sdrc_init(u32, u32);
 void get_board_mem_timings(u32 *mcfg, u32 *ctrla, u32 *ctrlb, u32 *rfr_ctrl,
 		u32 *mr);
+void identify_nand_chip(int *mfr, int *id);
 void emif4_init(void);
 void gpmc_init(void);
 void enable_gpmc_cs_config(const u32 *gpmc_config, struct gpmc_cs *cs, u32 base,