It turns out the prescaler fields in OST_CTRL are 2 bits wide,
not 3. The programming manual (as usual) is ambiguous and its
diagram shows 2-bit wide fields, but the bit positions in the
text give a 3-bit wide field. Ingenic's Linux code and my own
testing shows that they are, in fact, 2 bits wide.
This caused the OST2 divisor to be 16 instead of 4; the OST1
divisor was correct. This means that all udelay/mdelay calls
took 4x longer than they should've. After this change the OST2
prescaler will be 4, as intended, and udelay/mdelay calls will
wait for the intended duration.
Change-Id: I2ac0a9190f49b59a840c649bf586131f5f9fde82
