drm/exynos: fix comparison to bitshift when dealing with a mask

[ Upstream commit 1293b6191010672c0c9dacae8f71c6f3e4d70cbe ]

Due to a typo, the mask was destroyed by a comparison instead of a bit
shift.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>