usb: musb: Do not use musb_read[b|w] / _write[b|w] wrappers in generic fifo functions

The generic fifo functions already use non wrapped accesses in various
cases through the iowrite#_rep functions, and all platforms which override
the default musb_read[b|w] / _write[b|w] functions also provide their own
fifo access functions, so we can safely drop the unnecessary indirection
from the fifo access functions.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>