Convert CONFIG_OMAP3_SPI to Kconfig

This converts the following to Kconfig:
   CONFIG_OMAP3_SPI

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Minor comment tweaks]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/omap3_zoom1_defconfig b/configs/omap3_zoom1_defconfig
index 1b6eb30..03b4f00 100644
--- a/configs/omap3_zoom1_defconfig
+++ b/configs/omap3_zoom1_defconfig
@@ -34,5 +34,6 @@
 CONFIG_MMC_OMAP_HS=y
 CONFIG_NAND=y
 CONFIG_SYS_NS16550=y
+CONFIG_OMAP3_SPI=y
 CONFIG_FAT_WRITE=y
 CONFIG_OF_LIBFDT=y