uapi headers: simplify the <linux/compiler.h> stuff.

We don't really need <linux/compiler.h> and <linux/compiler_types.h>. We
already have a mechanism to remove unused macros, so let's do that. We
don't currently have a way to remove unused #includes, so we still need
<linux/compiler.h> and <linux/compiler_types.h> files (but I've clarified
the comments in them).

I've kept the empty definitions of `__user` and `__force` for source
compatibility. (We had one security test at least that was assuming
a kernel struct definition will "just work".)

Bug: http://b/262917450
Test: treehugger
Change-Id: Iacbbbc1aeef9a4fac52dabd7811ab875cc267d4f
diff --git a/libc/kernel/uapi/drm/radeon_drm.h b/libc/kernel/uapi/drm/radeon_drm.h
index 9dc69ad..3ec6bb3 100644
--- a/libc/kernel/uapi/drm/radeon_drm.h
+++ b/libc/kernel/uapi/drm/radeon_drm.h
@@ -479,7 +479,7 @@
   unsigned int clear_depth;
   unsigned int color_mask;
   unsigned int depth_mask;
-  drm_radeon_clear_rect_t __user * depth_boxes;
+  drm_radeon_clear_rect_t  * depth_boxes;
 } drm_radeon_clear_t;
 typedef struct drm_radeon_vertex {
   int prim;
@@ -498,20 +498,20 @@
   int idx;
   int discard;
   int nr_states;
-  drm_radeon_state_t __user * state;
+  drm_radeon_state_t  * state;
   int nr_prims;
-  drm_radeon_prim_t __user * prim;
+  drm_radeon_prim_t  * prim;
 } drm_radeon_vertex2_t;
 typedef struct drm_radeon_cmd_buffer {
   int bufsz;
-  char __user * buf;
+  char  * buf;
   int nbox;
-  struct drm_clip_rect __user * boxes;
+  struct drm_clip_rect  * boxes;
 } drm_radeon_cmd_buffer_t;
 typedef struct drm_radeon_tex_image {
   unsigned int x, y;
   unsigned int width, height;
-  const void __user * data;
+  const void  * data;
 } drm_radeon_tex_image_t;
 typedef struct drm_radeon_texture {
   unsigned int offset;
@@ -519,10 +519,10 @@
   int format;
   int width;
   int height;
-  drm_radeon_tex_image_t __user * image;
+  drm_radeon_tex_image_t  * image;
 } drm_radeon_texture_t;
 typedef struct drm_radeon_stipple {
-  unsigned int __user * mask;
+  unsigned int  * mask;
 } drm_radeon_stipple_t;
 typedef struct drm_radeon_indirect {
   int idx;
@@ -552,7 +552,7 @@
 #define RADEON_PARAM_NUM_Z_PIPES 17
 typedef struct drm_radeon_getparam {
   int param;
-  void __user * value;
+  void  * value;
 } drm_radeon_getparam_t;
 #define RADEON_MEM_REGION_GART 1
 #define RADEON_MEM_REGION_FB 2
@@ -560,7 +560,7 @@
   int region;
   int alignment;
   int size;
-  int __user * region_offset;
+  int  * region_offset;
 } drm_radeon_mem_alloc_t;
 typedef struct drm_radeon_mem_free {
   int region;
@@ -572,7 +572,7 @@
   int start;
 } drm_radeon_mem_init_heap_t;
 typedef struct drm_radeon_irq_emit {
-  int __user * irq_seq;
+  int  * irq_seq;
 } drm_radeon_irq_emit_t;
 typedef struct drm_radeon_irq_wait {
   int irq_seq;