usb: musb: merge musbhsdma.h into musbhsdma.c

Now Blackfin support is removed, header musbhsdma.h is only included in
musbhsdma.c. So let's merge the content in musbhsdma.h to musbhsdma.c
and delete musbhsdma.h.

Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>