drm/gem: Take reservation lock for vmap/vunmap operations

drm/gem: Take reservation lock for vmap/vunmap operations

The new common dma-buf locking convention will require buffer importers
to hold the reservation lock around mapping operations. Make DRM GEM core
to take the lock around the vmapping operations and update DRM drivers to
use the locked functions for the case where DRM core now holds the lock.
This patch prepares DRM core and drivers to the common dynamic dma-buf
locking convention.

Acked-by: Christian König <[email protected]>
Signed-off-by: Dmitry Osipenko <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]