musb: am335x: disable bulk split-combine feature

musb: am335x: disable bulk split-combine feature

On TI AM335x devices, MUSB has bulk split/combine feature enabled
in the ConfigData register, but the current MUSB driver does not
support it yet. Therefore, disable the feature for now, until the
driver adds the support.

One usecase which is broken because of this feature is that Ether
gadget stops working in Fullspeed mode (by un-defining
CONFIG_USB_GADGET_DUALSPEED)

After desabled this feature, MUSB driver send packets in proper size
(no more than 64 bytes) in Fullspeed mode.

This has been validated with Ether gadget in Fullspeed mode on AM335x
EVM.

Signed-off-by: Bin Liu <b-liu@ti.com>