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/coff.h b/libc/kernel/uapi/linux/coff.h
index be2db26..8f93b61 100644
--- a/libc/kernel/uapi/linux/coff.h
+++ b/libc/kernel/uapi/linux/coff.h
@@ -16,6 +16,8 @@
  ***
  ****************************************************************************
  ****************************************************************************/
+#ifndef _UAPI_LINUX_COFF_H
+#define _UAPI_LINUX_COFF_H
 #define E_SYMNMLEN 8
 #define E_FILNMLEN 14
 #define E_DIMNUM 4
@@ -193,3 +195,4 @@
 #define COFF_DEF_BSS_SECTION_ALIGNMENT 4
 #define COFF_DEF_TEXT_SECTION_ALIGNMENT 4
 #define COFF_DEF_SECTION_ALIGNMENT 4
+#endif