nand: mxc: Switch NAND SPL to generic SPL

This also fixes support for mx31pdk and tx25, which had been broken by commit
e05e5de7fae5bec79617e113916dac6631251156.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Acked-by: Scott Wood <scottwood@freescale.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
diff --git a/boards.cfg b/boards.cfg
index 1acf56a..860d8f1 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -45,7 +45,7 @@
 imx31_phycore_eet            arm         arm1136     imx31_phycore       -              mx31         imx31_phycore:IMX31_PHYCORE_EET
 qong                         arm         arm1136     -                   davedenx       mx31
 mx31ads                      arm         arm1136     -                   freescale      mx31
-mx31pdk                      arm         arm1136     -                   freescale      mx31         mx31pdk:NAND_U_BOOT
+mx31pdk                      arm         arm1136     -                   freescale      mx31
 tt01                         arm         arm1136     -                   hale           mx31
 imx31_litekit                arm         arm1136     -                   logicpd        mx31
 flea3                        arm         arm1136     -                   CarMediaLab    mx35