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/scsi/scsi_netlink.h b/libc/kernel/uapi/scsi/scsi_netlink.h
index ad6e52f..2e1b6cf 100644
--- a/libc/kernel/uapi/scsi/scsi_netlink.h
+++ b/libc/kernel/uapi/scsi/scsi_netlink.h
@@ -24,12 +24,12 @@
 #define SCSI_NL_GRP_FC_EVENTS (1 << 2)
 #define SCSI_NL_GRP_CNT 3
 struct scsi_nl_hdr {
-  uint8_t version;
-  uint8_t transport;
-  uint16_t magic;
-  uint16_t msgtype;
-  uint16_t msglen;
-} __attribute__((aligned(sizeof(uint64_t))));
+  __u8 version;
+  __u8 transport;
+  __u16 magic;
+  __u16 msgtype;
+  __u16 msglen;
+} __attribute__((aligned(sizeof(__u64))));
 #define SCSI_NL_VERSION 1
 #define SCSI_NL_MAGIC 0xA1B2
 #define SCSI_NL_TRANSPORT 0
@@ -39,10 +39,10 @@
 #define SCSI_NL_MSGALIGN(len) (((len) + 7) & ~7)
 struct scsi_nl_host_vendor_msg {
   struct scsi_nl_hdr snlh;
-  uint64_t vendor_id;
-  uint16_t host_no;
-  uint16_t vmsg_datalen;
-} __attribute__((aligned(sizeof(uint64_t))));
+  __u64 vendor_id;
+  __u16 host_no;
+  __u16 vmsg_datalen;
+} __attribute__((aligned(sizeof(__u64))));
 #define SCSI_NL_VID_TYPE_SHIFT 56
 #define SCSI_NL_VID_TYPE_MASK ((__u64) 0xFF << SCSI_NL_VID_TYPE_SHIFT)
 #define SCSI_NL_VID_TYPE_PCI ((__u64) 0x01 << SCSI_NL_VID_TYPE_SHIFT)