USB: AM35x: Add musb support

AM35x has musb interface (version 1.8) and uses CPPI41 DMA engine.
It has USB phy built inside the IP itself.

Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-omap@vger.kernel.org
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>