icE1usb fw: fix usb cdc notification struct attributes

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Change-Id: I7323c335c7cefe30446fb560b9381a3519b65f12
diff --git a/firmware/ice40-riscv/icE1usb/usb_gps.c b/firmware/ice40-riscv/icE1usb/usb_gps.c
index 7ca89fd..f2b09b4 100644
--- a/firmware/ice40-riscv/icE1usb/usb_gps.c
+++ b/firmware/ice40-riscv/icE1usb/usb_gps.c
@@ -49,7 +49,7 @@
 struct usb_cdc_notif_serial_state {
 	struct usb_ctrl_req hdr;
 	uint16_t bits;
-};
+} __attribute__((packed,aligned(4)));
 
 
 static void