spl, nand: add option CONFIG_SPL_NAND_IDENT to lookup for supported NAND chips

Add the config option `CONFIG_SPL_NAND_IDENT` for using the NAND chip ID list
to identify the NAND flash in SPL.

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
diff --git a/README b/README
index fb331f9..b1ddf89 100644
--- a/README
+++ b/README
@@ -2625,6 +2625,10 @@
 		CONFIG_SPL_NAND_DRIVERS
 		SPL uses normal NAND drivers, not minimal drivers.
 
+		CONFIG_SPL_NAND_IDENT
+		SPL uses the chip ID list to identify the NAND flash.
+		Requires CONFIG_SPL_NAND_BASE.
+
 		CONFIG_SPL_NAND_ECC
 		Include standard software ECC in the SPL