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>
Signed-off-by: Michal Marek <mmarek@suse.cz>