drm/omap: fix dmabuf mmap for dma_alloc'ed buffers

drm/omap: fix dmabuf mmap for dma_alloc'ed buffers

[ Upstream commit 9fa1d7537242bd580ffa99c4725a0407096aad26 ]

omap_gem_dmabuf_mmap() returns an error (with a WARN) when called for a
buffer which is allocated with dma_alloc_*(). This prevents dmabuf mmap
from working on SoCs without DMM, e.g. AM4 and OMAP3.

I could not find any reason for omap_gem_dmabuf_mmap() rejecting such
buffers, and just removing the if() fixes the limitation.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>