ddr: altera: use KBUILD_BASENAME instead of __FILE__

The KBUILD_BASENAME contains just the name of the compiled module,
in this case 'sequencer', rather than a full path to the compiled
file. Use it to prevent pulling the full path into the U-Boot binary,
which is useless and annoying.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Siew Chin Lim <elly.siew.chin.lim@intel.com>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Cc: Tien Fong Chee <tien.fong.chee@intel.com>