memory: omap-gpmc: make it explicitly non-modular

The Kconfig currently controlling compilation of this code is:

drivers/memory/Kconfig:config OMAP_GPMC
drivers/memory/Kconfig:  bool

...meaning that it currently is not being built as a module by anyone.

Lets remove the modular code that is essentially orphaned, so that
when reading the driver there is no doubt it is builtin-only.

Since module_init was not in use by this code, the init ordering
remains unchanged with this commit.

Also note that MODULE_DEVICE_TABLE is a no-op for non-modular code.

We don't replace module.h with init.h since the file already has that.

Cc: Roger Quadros <rogerq@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: linux-omap@vger.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>