ARM: OMAP: Fix consistent_sync properly

Turns out the problem was not in consistent_sync(), but blockops.c
overriding the the dmac_ functions with buggy ones... Undo previous
commit a9a31cc4ef3830e31766f03f55daa4b43e1d6dac, and remove blockops.c
from Makefile until it's completely removed from mainline kernel.