drm: meson: mask value when writing bits relaxed

The value used in the macro writel_bits_relaxed has to be masked since
we don't want change the bits outside the mask.

Signed-off-by: Julien Masson <jmasson@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/86y31r82fo.fsf@baylibre.com

drivers/gpu/drm/meson/meson_registers.h

@@ -12,7 +12,7 @@
 #define _REG(reg)	((reg) << 2)
 
 #define writel_bits_relaxed(mask, val, addr) \
-	writel_relaxed((readl_relaxed(addr) & ~(mask)) | (val), addr)
+	writel_relaxed((readl_relaxed(addr) & ~(mask)) | ((val) & (mask)), addr)
 
 /* vpp2 */
 #define VPP2_DUMMY_DATA 0x1900