build.py: revert counter on MMC (we'll need the pins for edid.py)

This reverts commit c51bcebc36df95c123dec3cb3c6ff2ceb3d2c630.
Makefile: fix top.bit location; add "run" and "poll" target
Makefile: build/top.bit depends on edid.py, too
output I2C bit counter on MMC