drm/omap: drop unneeded locking from mgr_fld_write()

drm/omap: drop unneeded locking from mgr_fld_write()

Commit c9e583aa654d099aff0fafd453d07b91b78fe03c ("OMAPDSS: DISPC: lock
access to DISPC_CONTROL & DISPC_CONFIG") added locking to
mgr_fld_write(). This was needed in omapfb times due to lack of good
locking, especially in the case of both V4L2 and fbdev layers using the
DSS driver.

This is not needed for omapdrm, so we can remove the locking.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190930103840.18970-2-tomi.valkeinen@ti.com