games/Bugdom2: fix build on powerpc*

/wrkdirs/usr/ports/games/Bugdom2/work/Bugdom2-4.0.0/Source/3D/3DMath.c:1541:5: error: assigning to '__vector float' (vector of 4 'float' values) from incompatible type 'int'

C3 = vec_madd( vec_splat( A3, 2 ), B3, C3 );
   ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~