mtd: mtdram: Expose module parameters

Since we can set module parameters also when a driver is built in,
it makes no sense to protect module parameter with #ifdef MODULE.
Now the mtdram sizes can also set when the module is not a loadable
module.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Boris Brezillon <bbrezillon@kernel.org>