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/can/gw.h b/libc/kernel/uapi/linux/can/gw.h
index 9be6107..f76bafb 100644
--- a/libc/kernel/uapi/linux/can/gw.h
+++ b/libc/kernel/uapi/linux/can/gw.h
@@ -47,23 +47,35 @@
   CGW_DELETED,
   CGW_LIM_HOPS,
   CGW_MOD_UID,
+  CGW_FDMOD_AND,
+  CGW_FDMOD_OR,
+  CGW_FDMOD_XOR,
+  CGW_FDMOD_SET,
   __CGW_MAX
 };
 #define CGW_MAX (__CGW_MAX - 1)
 #define CGW_FLAGS_CAN_ECHO 0x01
 #define CGW_FLAGS_CAN_SRC_TSTAMP 0x02
 #define CGW_FLAGS_CAN_IIF_TX_OK 0x04
+#define CGW_FLAGS_CAN_FD 0x08
 #define CGW_MOD_FUNCS 4
 #define CGW_MOD_ID 0x01
 #define CGW_MOD_DLC 0x02
+#define CGW_MOD_LEN CGW_MOD_DLC
 #define CGW_MOD_DATA 0x04
-#define CGW_FRAME_MODS 3
+#define CGW_MOD_FLAGS 0x08
+#define CGW_FRAME_MODS 4
 #define MAX_MODFUNCTIONS (CGW_MOD_FUNCS * CGW_FRAME_MODS)
 struct cgw_frame_mod {
   struct can_frame cf;
   __u8 modtype;
 } __attribute__((packed));
+struct cgw_fdframe_mod {
+  struct canfd_frame cf;
+  __u8 modtype;
+} __attribute__((packed));
 #define CGW_MODATTR_LEN sizeof(struct cgw_frame_mod)
+#define CGW_FDMODATTR_LEN sizeof(struct cgw_fdframe_mod)
 struct cgw_csum_xor {
   __s8 from_idx;
   __s8 to_idx;