drivercore: Generalize module_platform_driver

This patch generalizes the module_platform_driver macro and introduces a new
module_driver macro. The module_driver macro takes a driver name, a register
and a unregister function for this driver type. Using these it construct the
module init and exit sections which register and unregister the driver. Since
such init/exit sections are commonly found in drivers this macro can be used
to eliminate a lot of boilerplate code.

The macro is not intended to be used by driver modules directly, instead it
should be used to generate bus specific macros for registering drivers like
the module_platform_driver macro.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>