leds: make triggers explicitly non-modular

The Kconfig currently controlling compilation of this code is:

drivers/leds/trigger/Kconfig:menuconfig LEDS_TRIGGERS
drivers/leds/trigger/Kconfig:   bool "LED Trigger support"

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

Lets remove the couple traces of modular infrastructure use, so that
when reading the driver there is no doubt it is builtin-only.

We also delete the MODULE_LICENSE tag etc. since all that information
is already contained at the top of the file in the comments.

We don't replace module.h with init.h since the file doesn't need that.
However it does use EXPORT_SYMBOL, so we add the export.h header.

Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: linux-leds@vger.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>