imx: Add u-boot-with-nand-spl.imx make target

This image combines the SPL with the i.MX header, the FCB and U-Boot.

For i.MX25/35/51, the FCB is ignored by the boot ROM, so this image is just
useful because it can be programmed on a NAND Flash page boundary.

For i.MX53, the FCB is required by the boot ROM.

This does not support i.MX6 so far because its FCB is more complicated.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
diff --git a/.gitignore b/.gitignore
index e42d837..ed21203 100644
--- a/.gitignore
+++ b/.gitignore
@@ -31,6 +31,7 @@
 /u-boot.hex
 /u-boot.imx
 /u-boot-with-spl.imx
+/u-boot-with-nand-spl.imx
 /u-boot.map
 /u-boot.srec
 /u-boot.ldr