spl/85xx: new SPL support

Update CONFIG_RAMBOOT and CONFIG_NAND_SPL references to accept CONFIG_SPL
and CONFIG_SPL_BUILD, respectively.  CONFIG_NAND_SPL can be removed once
the last mpc85xx nand_spl target is gone.

CONFIG_RAMBOOT will need to remain for other use cases, but it doesn't
seem right to overload it for meaning SPL as well as nand_spl does.  Even
if it's somewhat appropriate for the main u-boot, the SPL itself isn't
(necessarily) ramboot, and we don't have separate configs for SPL and
main u-boot.  It was also inconsistent, as other platforms such as
mpc83xx didn't use CONFIG_RAMBOOT in this way.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: Andy Fleming <afleming@freescale.com>
diff --git a/doc/README.mpc85xx b/doc/README.mpc85xx
index 5a4b591..f9b023f 100644
--- a/doc/README.mpc85xx
+++ b/doc/README.mpc85xx
@@ -26,7 +26,7 @@
 ----------------------------------------------
 
 NOR boot
-		!defined(CONFIG_SYS_RAMBOOT)
+		!defined(CONFIG_SYS_RAMBOOT) && !defined(CONFIG_SPL)
 NOR boot Secure
 		!defined(CONFIG_SYS_RAMBOOT) && defined(CONFIG_SECURE_BOOT)
 RAMBOOT(SD, SPI & NAND boot)