Changes for GPMC (General Purpose Memory Controller) that take it
closer for being just a regular device driver.

Remove the ancient omap specific atags that are no longer needed.

At some point we were planning to pass the bootloader information
with custom atags that did not work out too well.

There's no need for these any longer as the kernel has been booting
fine without them for quite some time. And Now we have device tree
support that can be used instead.