video/omap: fix modular build

The framebuffer layer can be a loadable module, which forces
omapfb to be a module as well. However, this breaks the lcd
drivers, which are linked into the omapfb driver but each
have their own module_init() function. To solve this,
we split out the lcd drivers into separate modules and
export omapfb_register_panel, which is the only interface
required between the main omapfb driver and the lcd panel
drivers.

We also have to introduce a new Kconfig symbol for H3, since
that lcd driver has a dependency on TPS65010, which we can
express better in Kconfig than Makefile syntax.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-fbdev@vger.kernel.org
Cc: linux-omap@vger.kernel.org
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>