Convert CONFIG_SPI to Kconfig

This converts the following to Kconfig:
   CONFIG_SPI

This partly involves updating code that assumes that CONFIG_SPI implies
things that are specific to the MPC8xx SPI driver.  For now, just update
the CONFIG tests.  This also involves reworking the default for
CONFIG_SYS_DEF_EEPROM_ADDR so that we don't set it when we cannot make a
reasonable default, as it does not cause any compile failures.

Signed-off-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/Kconfig b/arch/Kconfig
index e599e7a..dd5a887 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -75,6 +75,7 @@
 	select DM_GPIO
 	select DM_MMC
 	select HAVE_BLOCK_DEVICE
+	select SPI
 	select LZO
 	imply CMD_GETTIME
 	imply CMD_HASH