dmadev: add missing header include

dmadev: add missing header include

When checking C++ compatibility of SDK headers,
an error is detected by the compiler:

lib/dmadev/rte_dmadev_pmd.h:95:23: error:
‘RTE_DEV_NAME_MAX_LEN’ undeclared here (not in a function)

The header file rte_dev.h must be included.

Fixes: b36970f2e13e ("dmadev: introduce DMA device library")
Cc: stable@dpdk.org
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Conor Walsh <conor.walsh@intel.com>