kgsl/drm: Add prime feature for fd handling.

This patch adds prime feature to support ion fd handle.
kgsl_drm have vendor specific ioctl instead of standard.
but If this patch applied in kgsl. we can use common libdrm api.

Change-Id: I2c73ea718dd72ec307e70ee2c3d3281083aef92c
Signed-off-by: Eunchul Kim <chulspro.kim@samsung.com>
Signed-off-by: Taeheon Kim <th908.kim@samsung.com>
Signed-off-by: Mathew Karimpanal <kjmathew@codeaurora.org>
(cherry picked from commit 088c500b9cf7097655161d21cc0f524c2e72ea48)