usb: musb: host: move DMA engine check from musb_tx_dma_set_mode_cppi_tusb() to its caller

Commit 754fe4a9 ("usb: musb: Remove ifdefs for TX DMA for musb_host.c")
looks incomplete: the DMA engine checks are  done outside the Mentor/UX500
handler  but inside the CPPI/TUSB handler. Move the checks out of the CPPI/
TUSB handler into its caller, musb_tx_dma_program().

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
[b-liu@ti.com: revise subject prefix]
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>