musb_hdrc: Fix TUSB sync DMA burst access

It seems like some values in docs are should be in fclk cycles
instead of nanoseconds.

At least these values seem to work.

Also make GPIO to be input for interrupt.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>