am335x_evm: Add support for the NOR module on the memory cape

This patch adds support for the NOR module that attaches
to the memory cape for a Beaglebone board. This does not
add booting support; only support so that you can boot from
SD/MMC and see the NOR module so that it can be programmed.

Signed-off-by: Steve Kipisz <s-kipisz2@ti.com>
[trini: Clean up config changes slightly]
Signed-off-by: Tom Rini <trini@ti.com>