pmcraid: Drop __DATE__ usage

The kernel already prints its build timestamp during boot, no need to
repeat it in random drivers and produce different object files each
time.

Cc: Anil Ravindranath <anil_ravindranath@pmc-sierra.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Michal Marek <mmarek@suse.cz>