usb: musb: Remove unused function declarations

Commit 32fee1df ("usb: musb: remove unused davinci support")
removed these implementations but leave declaration.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20230807140928.35932-1-yuehaibing@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>