drivers/usb/musb/musb_udc.c: Fix GCC 4.6 warning

Fix:
musb_udc.c: In function 'musb_peri_softconnect':
musb_udc.c:166:14: warning: variable 'intrtx' set but not used
[-Wunused-but-set-variable]
musb_udc.c:166:6: warning: variable 'intrrx' set but not used
[-Wunused-but-set-variable]
musb_udc.c:165:5: warning: variable 'intrusb' set but not used
[-Wunused-but-set-variable]

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Remy Bohmer <linux@bohmer.net>
Acked-by: Remy Bohmer <linux@bohmer.net>
Acked-by: Marek Vasut <marek.vasut@gmail.com>