usb: musb: USB_TI_CPPI41_DMA requires dmaengine support

The CPPI-4.1 driver selects TI_CPPI41, which is a dmaengine
driver and that may not be available when CONFIG_DMADEVICES
is not set:

warning: (USB_TI_CPPI41_DMA) selects TI_CPPI41 which has unmet direct dependencies (DMADEVICES && ARCH_OMAP)

This adds an extra dependency to avoid generating warnings in randconfig
builds. Ideally we'd remove the 'select' statement, but that has the
potential to break defconfig files.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 411dd19c ("usb: musb: Kconfig: Select the DMA driver if DMA mode of MUSB is enabled")
Signed-off-by: Felipe Balbi <balbi@ti.com>