Revert "dma-buf: refactor dma-buf name"

This reverts commit 00a53a39. The change
breaks DMA_BUF_SET_NAME ioctl by improperly duplicating the dma_buf
struct field 'const char *name'.

Signed-off-by: Will McVicker <willmcvicker@google.com>
Bug: 153823050
Test: boot bramble, verify list of probed devices
Change-Id: I716513d1e19449616eaa368d2c7de48ce479df3e