usb: musb: fix reset issue with full speed device

TXMAXP register is not getting programmed correctly for a full speed device
as can_bulk_split() have been removed by
"06624818: usb: musb: disable double buffering when it's broken" patch.

Adding back the case for can_bulk_split() to fix the reset message seen with
a full speed stick.

Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>