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/sound/asequencer.h b/libc/kernel/uapi/sound/asequencer.h
index 0076933..01a5058 100644
--- a/libc/kernel/uapi/sound/asequencer.h
+++ b/libc/kernel/uapi/sound/asequencer.h
@@ -209,9 +209,9 @@
 #define SNDRV_SEQ_CLIENT_DUMMY 14
 #define SNDRV_SEQ_CLIENT_OSS 15
 typedef int __bitwise snd_seq_client_type_t;
-#define NO_CLIENT ((__force snd_seq_client_type_t) 0)
-#define USER_CLIENT ((__force snd_seq_client_type_t) 1)
-#define KERNEL_CLIENT ((__force snd_seq_client_type_t) 2)
+#define NO_CLIENT (( snd_seq_client_type_t) 0)
+#define USER_CLIENT (( snd_seq_client_type_t) 1)
+#define KERNEL_CLIENT (( snd_seq_client_type_t) 2)
 #define SNDRV_SEQ_FILTER_BROADCAST (1U << 0)
 #define SNDRV_SEQ_FILTER_MULTICAST (1U << 1)
 #define SNDRV_SEQ_FILTER_BOUNCE (1U << 2)