mtd: denali: Drop print of build date/time

The kernel already has this information, and individual drivers
shouldn't duplicate that.  This also eliminates the use of __DATE__ and
__TIME__, which make the build non-deterministic.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>