sunxi_nand_spl: Rename SPL_NAND_SUNXI to NAND_SUNXI

We eventually want to add full nand support, since it makes no sense
to build SPL with nand support and u-boot without, or the other way
around, a single option will suffice.

Renaming the Kconfig option now makes things easier when we add full
nand support in the future.

The "obj-$(CONFIG_NAND_SUNXI) += sunxi_nand_spl.o" is moved to an
"ifdef CONFIG_SPL_BUILD" block in the Makefile.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index 09c9668..1d08d28 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -63,6 +63,14 @@
 	  This enables the driver for the NAND flash device found on
 	  PXA3xx processors (NFCv1) and also on Armada 370/XP (NFCv2).
 
+config NAND_SUNXI
+	bool "Support for NAND on Allwinner SoCs in SPL"
+	depends on MACH_SUN4I || MACH_SUN5I || MACH_SUN7I
+	select SYS_NAND_SELF_INIT
+	---help---
+	Enable support for NAND. This option allows SPL to read from
+	sunxi NAND using DMA transfers.
+
 comment "Generic NAND options"
 
 # Enhance depends when converting drivers to Kconfig which use this config
@@ -92,18 +100,10 @@
 	  This is a small implementation of the Denali NAND controller
 	  for use on SPL.
 
-config SPL_NAND_SUNXI
-	bool "Support for NAND on Allwinner SoCs in SPL"
-	depends on MACH_SUN4I || MACH_SUN5I || MACH_SUN7I
-	select SYS_NAND_SELF_INIT
-	---help---
-	Enable support for NAND. This option allows SPL to read from
-	sunxi NAND using DMA transfers.
-
 config NAND_SUNXI_SPL_SYNDROME_PARTITIONS_END
 	hex "Size of syndrome partitions in sunxi NAND"
 	default 0x400000
-	depends on SPL_NAND_SUNXI
+	depends on NAND_SUNXI
 	---help---
 	End address for boot partitions on NAND. Those partitions have a
 	different random seed that has to match the sunxi BROM setting.