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/pxm2_defconfig b/configs/pxm2_defconfig
index 5bceca7..2422ed4 100644
--- a/configs/pxm2_defconfig
+++ b/configs/pxm2_defconfig
@@ -64,6 +64,7 @@
 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT=1
 CONFIG_PHYLIB=y
 CONFIG_SYS_NS16550=y
+CONFIG_OMAP3_SPI=y
 CONFIG_USB=y
 CONFIG_USB_MUSB_HOST=y
 CONFIG_USB_MUSB_GADGET=y