USB: musb: fix build error introduced by isoc change

The recent commit "usb: musb: Fix for isochronous IN transfer" (f82a689f)
seems to have been against an older kernel version.  It uses the old style
naming of variables.  Unfortunately, this breaks building for most MUSB
users out there since "bDesiredMode" has been renamed to "desired_mode".

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Felipe Balbi <felipe.balbi@nokia.com>
Acked-by: Anand Gadiyar <gadiyar@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>