Update to android-mainline kernel headers v5.4.

Update generate_uapi_headers.sh to checkout the android mainline
kernel. Also, add a small modification to look for the kernel directory
in common not linux-stable.

Remove deprecated android headers from android/uapi/linux. Also,
remove f_accessory.h since it's in the android mainline kernel.

Test: Builds and runs on walleye.
Change-Id: Ia371305e19f56e6bcc2db6d5b4d299819f07ffc6
diff --git a/libc/kernel/uapi/linux/cryptouser.h b/libc/kernel/uapi/linux/cryptouser.h
index b32db64..1d145bd 100644
--- a/libc/kernel/uapi/linux/cryptouser.h
+++ b/libc/kernel/uapi/linux/cryptouser.h
@@ -16,6 +16,8 @@
  ***
  ****************************************************************************
  ****************************************************************************/
+#ifndef _UAPI_LINUX_CRYPTOUSER_H
+#define _UAPI_LINUX_CRYPTOUSER_H
 #include <linux/types.h>
 enum {
   CRYPTO_MSG_BASE = 0x10,
@@ -168,3 +170,4 @@
   char type[CRYPTO_MAX_NAME];
 };
 #define CRYPTO_REPORT_MAXSIZE (sizeof(struct crypto_user_alg) + sizeof(struct crypto_report_blkcipher))
+#endif