usb: musb: tusb6010_omap: fix build failure: error: 'musb' undeclared

  CC      drivers/usb/musb/tusb6010_omap.o
drivers/usb/musb/tusb6010_omap.c: In function 'tusb_omap_use_shared_dmareq':
drivers/usb/musb/tusb6010_omap.c:92: error: 'musb' undeclared (first use in this function)
drivers/usb/musb/tusb6010_omap.c:92: error: (Each undeclared identifier is reported only once
drivers/usb/musb/tusb6010_omap.c:92: error: for each function it appears in.)

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>