Convert musb fifo to 8bit to allow 8/16/32bit access

Convert musb fifo to 8bit to allow 8/16/32bit access

MUSB allows reading and writing to the fifo in 32/16/8 bit
width. The Linux kernel does this sometimes, most usually at
the end of writing the packet to allow packet to end at a
odd bytecount.

Convert the fifo to 8bit allows removing lots of shifts
which shows that the fifo is more natural as 8bit.