meson: do not mark exynos/omap/tegra as disabled features

Otherwise, using `--auto-features=enabled` wouldn't work because it
only "forces" auto options to be enabled.

This will enable these backends in CI to catch possible build errors.

Closes: https://gitlab.freedesktop.org/mesa/libdrm/-/work_items/128
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>

meson_options.txt

@@ -46,13 +46,11 @@ option(
 option(
   'omap',
   type : 'feature',
-  value : 'disabled',
   description : '''Enable support for OMAP's experimental KMS API.''',
 )
 option(
   'exynos',
   type : 'feature',
-  value : 'disabled',
   description : '''Enable support for EXYNOS's experimental KMS API.''',
 )
 option(
@@ -63,7 +61,6 @@ option(
 option(
   'tegra',
   type : 'feature',
-  value : 'disabled',
   description : '''Enable support for Tegra's experimental KMS API.''',
 )
 option(

omap/omap_drm.c

@@ -27,7 +27,6 @@
  */
 
 #include <stdlib.h>
-#include <linux/types.h>
 #include <errno.h>
 #include <sys/mman.h>
 #include <fcntl.h>