dri: add missing 16bits formats mapping

i965 advertises the 16-bit R and RG formats through
eglQueryDmaBufFormatsEXT but falls over when a client tries to use or
asks more information about such a format because
driImageFormatToGLFormat returns MESA_FORMAT_NONE.

Found by Eero Tamminen.

v2: Add G16R16 formats (Lionel)

v3: Fix G16R16 mapping to mesa format (Jason)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106642
Reviewed-by: Plamena Manolova <plamena.manolova@intel.com> (v2)
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/mesa/drivers/dri/common/dri_util.c

@@ -936,6 +936,22 @@ static const struct {
       .image_format = __DRI_IMAGE_FORMAT_SARGB8,
       .mesa_format  =        MESA_FORMAT_B8G8R8A8_SRGB,
    },
+   {
+      .image_format = __DRI_IMAGE_FORMAT_R16,
+      .mesa_format  =        MESA_FORMAT_R_UNORM16,
+   },
+   {
+      .image_format = __DRI_IMAGE_FORMAT_R16,
+      .mesa_format  =        MESA_FORMAT_L_UNORM16,
+   },
+   {
+      .image_format = __DRI_IMAGE_FORMAT_GR1616,
+      .mesa_format  =        MESA_FORMAT_R16G16_UNORM,
+   },
+   {
+      .image_format = __DRI_IMAGE_FORMAT_GR1616,
+      .mesa_format  =        MESA_FORMAT_L16A16_UNORM,
+   },
 };
 
 uint32_t